Let's say Mazda was making a next-gen rotary model, I'd like to know what would you change on the new car vs the older ones.
For me, the engine.
Whoa, calm down there, I didn't say swap out the rotary powerplant for a different type of engine, but rather: change the engine itself for a "better" rotary unit (by better, I mean a better design; the Dorito rotors keep wearing down too much for a road car in the long run), and maybe tie it in with the next-gen Skyactiv tech. This means having a system that doesn't rely as much on spark, and getting better fuel economy.
There was a startup that made rotary engines that could run on almost any fuel,
and its name escapes me EDIT: Liquidpiston, it had a different shaped rotor, that claims to be an inside-out Wankel.
And one question remains, "What would you change?"