Hyper car bodies (wide wheel fenders, super low 2 door hatchbacks that usually come with pop up wings)
W engines (from 12 to 28 (for those who want to experiment with them))
Rotary engines
Electric Motors
Hybrid option
Diesel/Used Cooking oil/Ethanol
Nitrous (for the special, non mass production race cars)
Super Chargers
Quad Turbochargers (BMW has an engine with it)
Compressed Air Superchargers
Interior design
Light Weight Titanium Alloys
Nano Carbon
Vacuums (Red Bull X and Chaparral have them for maximum traction, but maximum speed)
V10’s (the viper has one)
sigh *
Read the faq.
Must of what you ask is out of the scope of the game, because is dedicated to production cars, not racing cars.
W, rotary, diesel, hybrids, electrics will not be in the game (but V6, V8, V10, V12, L4, L6, boxer [not flat] 4 and 6 will be) because those would take too much time to be designed (around six months to a year each, counting the calcs, the UI design, the 3D assets), there is a YouTube video in the official account responding in depth why that would not happen.
I encourage you to read the faq before posting, and to use the search function, this game has been in developing quite a long time, so almost 95% of the suggestions people come up they have been already suggested.