You're going to get a host of opinions on this.

Mine is simple, Tamiya is expensive, but you get an extremely well engineered tank for your money. I run all mine completely OOB stock and with tanks that have been abused beyond anything a plastic model should endure, I have yet to have an issue with any of it in terms of design.

That said, you want to start doing things like adding metal tracks (completely unnecessary in my opinion), or add weight to increase ground pressure, yadda yadda yadda then you've gone beyond what it was designed for.

Go down that road, you should expect to pay for it. Bigger motors, gearboxes, bearings, springs, braces, stronger batteries, etc.

Perfect example of this is metal barrels. No elevation arm had any problem when the barrels in the kits were styrene. But Tamiya caved to the AM market catering to people who can't fix a seam, so they added aluminum barrels to their kits. So now the ABS elev arm rounds out under the weight as well as now you need an etching primer. Change the arm and when stressed, a nylon gear will round out. Change the gears and the motors is under stress at the limit. Add micro switches to stop the limits and look at where we are, back to what the tank was before we added a metal barrel.