To believe the X1/9 is a "Fiat" is shallow understanding of the history of this most significant and under appreciated design.
An interesting point of view.
I see where you are coming from but can't agree with the conclusion. If we follow your statement and apply the same to say, just cars out of Modena then the following is not Ferrari but Pininfarina’s if we follow just the 250 and who made the bodies I just get confused. There were many models and whilst Farina made most of the 250 bodies some were built by Bertone, Scaglietti and when the GT all became too much for Pinin he asked Mario Boano who then passed this to his so in law, hence the 250 GT Ellena. So are they not Ferrari 250's but something else?
To expand,
I doubt that many Americans would accept the Cadillac Allanté was a Pininfarina, where completed bodies — designed and made in Italy by Pininfarina were shipped 4,600 miles from Italy in specially equipped Boeing 747s about 50 odd at a time, to Cadillac's Detroit/Hamtramck Assembly plant where they were mated with domestically manufactured chassis and engines (a modified variant of the Caddy 4.1 liter V8). Going off your methodology they are Pininfarinas but I would call it a GM Caddy sold and marketed under the Cadillac banner, a good attempt by GM at having a go at the Merc' SL, despite the justified criticism inherent as a result of the dopey front wheel drive layout in such a large heavy car.
So I take your train of though and apply it to two more 'modern' cars with the entire production cycle for both cars at the Grugliasco factory, the Opel Astra Cabrio and the Fiat Punto Cabrio of the early-mid 1990's. Bertone or Opel / Fiat ? Taking that even further is the G'Wagen a Mercedes or a Styer. The G-Class is still in production after 35 years and is one of the longest produced Mercedes-Benz in Daimler's history. Only the Unimog surpasses it. It is made by Magna Steyr in Austria, the 'contract' was marked to expire this year.
Whilst the X 1/9 body was produced in Turin at the Bertone factory the shells were then transported to the Fiat's then massive 5 story Lingotto factory for final assembly (unless I got that all wrong). Just like the 850 spider before it the design was not without access to Fiats parts bin and engineers. Giuseppe Puleo did not work in isolation and had access from previous projects to Fiat engineers and the Primula/128 parts bin, it was never designed from scratch by him as the existing geometries and powertrain constraints of the existing 128 drawings had to be accommodated. He had room to tweak but no wholesale changes or the business case for using 128 parts to make the project viable would have been scuttled. I got the impression that you were saying that Gruppo Bertone created project X1/9 in isolation, not the case Fiat was actively envolved. Only after 1982, shortly after the introduction of the 1500 model when production tapered did complete production go to Bertone with models subsequently badged as the Bertone X 1/9.
You are onto something with the thought about the relationship Nuccio and Umberto had. Project X 1/9 was at the end of an era where coach builders took a 'ladder' chassis from say Alfa Romeo, Ferrari etc styled and 'clothed' it in metal and fitted an interior. Nuccio had done the 850 spyder and Fiat was looking for its replacement. What makes the X interesting in this sense is that it was a well developed and rigid unitary construction, designed from the beginning to meet the late 60s U.S. safety regulations, as this was where the industry was heading. Volvo was the only other to meet that target and it was rescinded. The Autobianchi geared concept by Fiat was shown on the Autobianchi stand in 68' but Bertones stunning futuristic design concept rekindled the idea but with 128 parts in mind when it was revealed at the motor show the year later 1969, this was the same year that the 128 was reaching realization and production the following year at the factory Fiat built especially for it North of Turin in Rivalta. I would offer Fiats arm, Autobianchi, made the original 'connection' that the components would make a mid engined sports car. It was probably Giacosa's idea but nothing came of it. Concepts from both OSI and from Fiats own design house were toyed with but came to nothing. That Nuccio offered mid engine when they asked for either front or rear engined design makes a connection that Fiat probably already knew of it but didn't have the skills. Fiat had 'field' tested this running gear on a previous production model, the Primula (hiding) under the Autobianchi badge so the running gear was proven and already known to work, not Bertone's design. The rear wishbones and stiffer front track rod are almost definitely Giuseppe as the 128 parts were not stiff enough and insufficient to control the steering angles/wheels.
A milestone in itself for Fiat as this laid the foundation for FWD layouts as we know them today. That Bertone pulled it off where OSI and Fiat didn't bringing so many design elements into a mass production car is testament to the Bertone Carrozzeria and the creative genius of Marcel Gandini (Giorgetto Giugiaro had gone to Ghia in 65'). Remember that this was before the Countach and Gandini was then a young, inexperienced designer. Totally inexperienced in the practical, ergonomic aspects of automobile design, but at the same time unhindered by them. The coach builder of old is all but a distant memory now and the artistic free spirit is now constrained, where once we had young fresh talented people like Gandini nurtured by the talent of maestros like Nuccio we have a designed by committee process. Perhaps that is why Serio had sent the new Alfa back for countless revision in a skunkworks to get the Icon car that is the new Guila.
https://web.archive.org/web/20091027072658/http://geocities.com/MotorCity/Downs/8835/
Sadly the concept cars seen today rarely have the same content in a final assembly line product. There are a huge amount of talented and creative folks out there but they are straight jacketed by the accountants at the car makers where they work. The costs of developing a vehicle and delivering it to market are so high that just a few duds can unwind the financial position of most car makers. This link gives a good idea to who is who and what is what in the modern world of car design. If you have a spare dollar it is worth at least the one year of subscription, I'd rather read CDN than Reuters or the Huffington post when I have time to read. Makes me think that there is hope of a creative future in a market where cars are becoming homogeneous mass of poop that looks unimaginative and far to darn conservative. Perhaps it is a reflection that the masses who buy them are boring conservatives.
http://www.cardesignnews.com/
As far as the old drawings from Gruppo Bertone I understand Lilli kept as much as she could, but the point is moot they are of historical value only. Your assertion is correct FCA would have to have rocks in its head to try and make pattern parts, the body was never theirs but as a completed vehicle it was. There is more to the collapse of Bertone than is seen at first glance, but in the end styling houses like Nuccio Bertones and Pinin Farina etc are relics of a system of car making that has long since transitioned to 'in house' design where the stylists move from one manufacturer to another. Not where manufacturers farm out projects to stylists. Their movements are often as interesting as the politics of Formula One but few know their names outside of the industry. Sad really as the vox popoli laud people who are famous for being famous, not what they are capable of creating due to their talents in science engineering or the arts. The things that really matter.
So without meaning to be disrespectful I put forward that to believe the Fiat X1/9 is a "Bertone" is shallow understanding of the history of Carrozzerias. In the North Americas the tradition of independent coachbuilders (styling houses) was not strong like it was in Europe. Ford and his model T brought about a different culture and fewer examples of collaboration with houses like Bertone, Ghia or Pininfarina were engaged, they exist but are few.
Without being a pesky contrarian I would like to think we can agree to disagree.
The X 1/9 was the replacement to the 850 spider that Fiat was looking for, Nuccio was asked to present a replacement to his 850 Spider design and offered a mid engined layout, perhaps the board were fixated on a front wheel drive to keep it simple in line with their as yet unreleased 128 so it could be built at Rivalta along the other 128's and disappointed they had a mid engined proposal before them but the business case for utilizing the 128 parts made sense. Perhaps that is why the production of the 124 spider continued on side by side as it would be odd to have two open top 4 cylinder two door cars from the same car maker, it sounds to me you are implying as if they were forced to build it at all. I doubt the management would have got in the old mans way unless there was a case as to why it would be a disaster. I am happy to change my opinion but I need to see where all the management protestations were, I remember none but happy if you point me at where I can find evidence of it. They did have other options before them with design drawings done in 1969 of Pininfarinas v6 Fiat X1/8 Project proposal. But we know that was suspended and transferred to Lancia where it surfaced as the 4 cylinder twin cam X1/20 some year or so later, probably due to cost and that the 124 spider was still selling, the 'Montecarlo' would have killed it. The X1/8 cost would have been a problem as it was not based on any existing production car. What I would say is when management eventually got their way decades later with the Fiat Barchetta it was derided as a FWD POS. The MX5/Miata kicked its ass into oblivion where project X1/9 created a format that was thought at the time to be impractical but set the benchmark for later mid engined examples like the MR2 etc. If what you are saying is correct then Umberto got it right, design by committee sucks and thank goodness they were 'forced' to go with project X1/9. That the X1/20 never got it's V6 from the original X1/8 concept is a crime.
The 850 spider body was designed by Giugiaro ( before he left as he wouldn't work with Gandini) and built by Bertone in its Grugliasco plant in Turin, I don't see anyone thinking that it is a Bertone and not a Fiat.
But lets leave it at this, Enzo liked the 128 platform so much he had one as a personal 'town car' to run around in. The oversquare engine and the driveline/suspension layout we love so much where you can wring the neck off the little engine to +7k RPM married to a masterpiece of coachwork by Gruppe Bertone created a masterpiece appreciated by a few who know the secret of that successful union.
Yesterdays squirt up the mountain was a hoot, I certainly appreciated that successful union. Cheshire cat grin was installed and it made me 'feel' good as it was a pleasure to drive through the twisties and squirt past the econoboxes chugging up the mountain.
Pity its raining today.