There was...(I thought they still were) a Dutch company who build new cars on Porsche 944 donor cars, I found them not bad and not expensive, but sadly after 17 cars they went bust I just saw...
anyway those cars built by Coachbuilders Heijndijk this is their Heijnsdijk 2500SF
But I don't think that Fran is interested in building off an older existing platform like the c4. I think that he prefers an updated, modern chassis and components. The c4 is something that FF would use :lipsrsealed: