Interesting RC conundrum with 104 and 103.
This much we all know, if you split the classes racing and participation in general will suffer.
The latest in RC is taken from the latest in full scale, so 104 and F10 should be the standard for racing along with tall & narrow rubber tires just like real F1. Solution is kind of ugly but the day of the 103 and other wide chassis F1s is over. That look no longer exist in real F1 so now you are racing a vintage class. if F1 cars change in a few years and HPI & Tamiya & others follow then RC racing should follow to stay current.
The only other and probably best solution would be sanctioning bodies coming up with class rules just like they did with touring cars but that's not in the cards for now.
As for different motor classes, bad idea again. Don't re-invent the wheel, take a page out of very successful RCGT, one motor and from there drivers' skills organically will split the classes. Dump the cheat prone brushed (it ruined 2wd mini cooper class for all) brushless only and a strict esc rule to go with no SPX etc.
Anyway happy racing