Changing motor winds is really the easiest option. Its cheaper than esc's and batteries and easy to tech. Even if you (roar) think that 21.5 will be as fast as 17.5 or faster in a year, I'd be more than willing to buy another motor in a year. I think most guys don't have a problem with buying a motor for a year.
I also like the idea of stock and mod. You could still run novice/sportsman stock and expert stock.
A roar approved esc standard is an option, but I personally don't like it. I like on road because it is difficult and there is just endless adjustments in everything. Go ahead and call me a nerd. But the more fine tuning, the better. Not to mention that this latest advancement is much better for the motors. We are able to gear light and the motors come off cooler.
Ruben, this is Louie. I said that so you would read this.