Ok before i answer your questions, first off: I agree a big rear motor might be better instead of 2x G series or in addition to a front G-series. BUT this is different subject.
I didn't mean to imply that the other 10% would be a problem, maybe more of an inconvenience. I think up to about 10% of the time (worst case scenario with different over all diameter or windings in motor etc) it could be sub-optimal. I think it would be tolerable and maybe even unnoticeable most of the time. As long as torque is kept down to reasonable levels in the front. Well tuned front suspension helps.
The inconveniences might present themselves when the rider was to hold the throttle at a certain level corresponding to the speed of the bike. Then one motor would turn off before the other and you would essentially feel the bike "getting up to speed twice" or backing off the power twice as each motor turned off at different RPMs. Even at low speeds this wouldn't really be a problem as long as torque was limited to low enough levels in the front motor.
I always like to encourage people playing around with 2WDs, I think it would be really cool to see the gradual development of 2WD bikes.
