Have you had a 10-round magazine permanently attached to an AR? Im kinda dubious about these kits to attach on our own. Thinking having it done by a gunsmith would be best.
Short of actually welding a metal mag in, that's the closest I can come up with to being permanent.
Anything else regardless of expoy in a nut hole, loctite on threads, all that is easily removed with tools.
Most people have made their peace that by installing a simple magazine lock, that they are in compliance with the law. It follows the spirit of the law by preventing magazines from readily being removed and inserted. You have affixed a magazine to the rifle.
Anything above and beyond attaching a simple mag lock, is no more permanent than just a mag lock is on its own.
But at the end of the day it's all comfort level, if you want to pay a gunsmith to do something, hey it's your money.