So, after looking at recent reply. There "seems" to be a problem on the Mod guy keep blowing up their motor and ESC. ("seems", cause there is no solid data provided)
I think it is the responsibility for the racer to keep the car running. If they blow up the motor, it is their business. It is the racer decision to make. Faster but easier to fail, a little bit slower but more robust. It is all their choice to make. We normally call this race strategy. If you break a motor, you make a wrong choice. (It is simply a part of the setup choice they have to make)
If a racer tends to blown up their ESC and motor when using 6 cells. There is a very high chance he will repeat the same mistake even if number of cells is limited, be it 4 or 5. (cause he is very smart on how to squeeze out the max speed from what they have
I think a better solution is to use a more robust motor or ESC. It may require a rule change on MOTOR/ESC. (or new product from RC manufacturer) But, even a more robust motor/esc have their limit and racer will make use of the new enveolpe to squeeze more speed out of the car very soon. So, next time, the limiting factor may be the chassis.
Anyway, it is not wise to slow down the mod class. What do you think if a mod car is the same speed as a 19T or even stock class. Will you like to be the driver of that mod car?
Here is a little shearing of how I got into this hobby:
I myself was attracted to touring car cause it "was" fast and it "was" exciting to race with other fast car. It was the mod (no-limit) racing which attract me to the hobby (though I'm running stock car now, the speed of stock car definitely will NOT attract me to start this hobby)
If it was not the fast car I saw, I would not spend hours here viewing those nonsense post to tell us how we should slow down our car.