I fully agree on the need for 40's, 50's, and 60's cars.
I'd also like to point out that it'd be nice to have some of the late 90's, early 00's aerodynamic compacts. And as I've mentioned before, it'd be nice to have something like the first-generation Insight and Prius, even if we can't do hybrids, because the designs are very aerodynamic. Especially if they were given more than just their 3-door/5-door hatch variants, and were brought into a full lineup (2-door coupe, 3-door hatch, 4-door sedan, and 5-door hatch).
We could also do with a mid-90's minivan. We currently have from the workshop one that fits late 80's to early 90's, and one that fits late 00's from in game.
Last, and in my opinion, least important, we could do with some older two-door supercars.