TL;DR: Nothing I'm about to discuss will help this years issues.
Well, how deep down the "hackable motor" path do you wanna go?
There's fixes for all of this. In fact, there's a whole r/c series that developed ~becasue~ of the motor wars. (I'm looking at you Can-Am)
Just to throw it out there. I like "motor claim" rules, especially on cheap motors. Heck force a motor claim on the top 10% of racers. I like "pots" of motors that get handed out for each race day. This just needs to be done ~enough~ that nobody will put the effort into tweaking motors anymore.
Another thought is to go with a "weird" motor. We already have fixed gearing. Getting a mass produced quadcopter motor is ... Well the rotor riot people are selling theirs for $25 each. Those motors can do 100's of watts. They should be very happy with the ~around 65watts~ we need for Mini, and Gt1. Instead of going to reedy and praying they can make motors, why not contract with one of the asian manufacturers, have them produce some motors with the shaft out the bottom. Maybe they could even integrate sensor boards.
Something tells me that could be done for less than $50 retail.