My idea would be 2 new panel materials :
Partial Carbon
Partial Plastic
Partial Carbon:
A less extreme version of the full CF option. It would be heavier than normal CF but easier and faster to produce and manufactor. It could be used for sportcars, trackcars and even highend economy vehicles.
Partial Plastic:
Cheap and easy to produce. And also cheap to replace but it would need a “Plastic molding” facility, has a low environmental resistance and impacts the prestige. Would be useful for budget vehicles.
Speaking of Renault, the first three generations of Espace were built around a liquid galvanised steel space frame clad with polymer body panels. Not necessarily the cheapest way, but impervious to dents and nearly impervious to rust. The fourth gen (like my glorious 2008) moved to a hybrid construction with a conventional steel monocoque, with movable body parts made from aluminium and bolt on parts such as bumpers and front fenders out of plastic. Always a good time kicking in the front wings with yo friends to see who can dent them in furthest. Which is also the currently most common method of body construction.
Incidentally both the Espace and Dustbuster’s construction were predated by lightweight, mid engined sports cars. The Talbot Matra Murena (1980) and Pontiac Fiero (1984).
Fibreglass is replaced by SMC once you get the SMC processing in the factory it is the not-hand-made version of fibreglass. So that will be in the LCV3 most likely.
With that many materials, it would really end up needing either a scrollable list or two lists, one of main and one of partial material choice like what Crossworks suggested. So… maybe too much effort, or “Treated Steel” Ends up short lived