Erik. The rules come from the ”Godfathers of motorsport” FIA with some differences in the national classes. You can like the rules or not but it must be better to have similar rules around the globe.
Welding or not? Well for many years ago you were forced to remove the rollbar after the rally when you used your car as a daily driver so you were not allowed to weld it.I think this was changed in the beginning of the 70ies here in Sweden. I tested my first rally V4 1973 with a rollbar at the Swedish ”Bilprovningen” and had a note in my registration papers for my car. Then it was OK to use the car daily with the rollbar mounted.