I agree, would be great to have these as "native" button-mappable functions in Settings/Controls, like other functions like Speed Limiter and such.
Of course, not an optimal substitute for the time being, but I've made a short and lazy script to adjust Brake Balance at least, using buttons on my wheel.
It's basically mimicking the button presses you would make on the keyboard (F11, left/right to adjust, F9 to go back to tyre temps overlay). See:
https://en.lfsmanual.net/wiki/Script_Guide#Brake_balance_adjustment_.28increase.2Fdecrease.29
Scripting in LFS opens up a lot of possibilities and I really think it's awesome, however, I agree that functions like these should be present natively and more accessible. Seasoned LFS players can probably manage to make scripts like this work, but someone who just joined LFS will spend a lot of time searching for a basic brake balance adjustment function.