Capping motor wind would create a class in itself, smaller mah and longer races is something that wouldn't help making it interesting. Longer races just mean you have to be with utmost concentration for even more time and less mah means you have to preserve battery or run more efficient electronics/car setup, that would make even less people capable of running them.
For me 1/12th mod would benefit from:
2s shorty batteries- more efficient, cheaper and widely available;
Capping rear spoiler height for decrease in downforce and tire wear, if not the race to higher and higher downforce will never end.
I think it's just that, bringing the speed down by having less "aero grip" and going to more efficient electronic setup would widen the target audience. About higher voltage, remember no one is prohibiting from running a boosted 3.5 with 2s voltage but that's not realistically possible so I think a "wind cap" or gentleman's agreement will ensue.