Agree entirely with the DeltaWing and the R18 TDi.
But the Reventon drives like a Murciélago so that's pointless, the R15 TDi has been made redundant by the R18 TDi, and the Vauxhall Insignia is a nice idea but we'd need a few more family cars on the game for it to fit in. If it came with a Mondeo, an Alfa 159, a C-Class Merc and so on, that'd be better.
e-Tron and Delta Wing, yes.
I'd like to see Vectors again - W-8, WX-3, WX-3R, and M-12. Miss them from GT-2.
The Renault Espace F1 would also be a good return, I think.