Theres really great stuff from the 60s, 70s, 80s and even 90s that could well be in rf2. I can think on group A cars, old dtm from early 90s, even some 80s street uno´s/G40/106/crx/etc would be fun. We have enough historic open wheelers in my opinion, we need some extra stuff. Howstons seems few for a glourious second half of century.
Some update to the cars would be great. Front tires at the Brabham Bt-20 looks disproportionate between ring and rubber. The rubber is too tall for that ring. An option with the BT-24 version with the second version of the engine would be great too.
66-67 GT cars: unlicensed () versions of the Ford MkI or II, the stunningly gorgeous Chaparral 2D (hey, American team ... maybe a license opportunity ), an updated Howston, Porsche 906/910, and a Ferrari 330 P3. Or any car driven by Cevert. Add Watkins Glen, Mosport, some other N. American track, and oh goody. ps: I'm no fan of GT or tintop racing with a very few specific exceptions... such as the aforementioned .
A true beautie.. Dont expect to see it licenced though, as Ferrari is not governed by the enthusiasts till the old man left, but by the greeders/grabbers..
This is the big distinction, rF2 accomplishes this in a wonderful manner. (had to say it, it's true).
Any and all of the above plus don't forget an ISI version of the T280 may be possible because licensing deal with Lola.
In another sim which I am assume is one of the sims you are referring to, I had the best time in the world according to one app and one of the best times in the world according to another app, using absolutely no aids in a full manual road-car, and never using the clutch for upshifts or downshifts, and literally hearing grinding noises on just about every downshift, so please don't go there.