There are plenty of ways to ensure that A.I infantry won’t be overpowered. The Infantry we had in the WWI event worked just fine and took like 1 or 2 shots to kill. The only “unkillable god” AI I’ve encountered were tanks in assault arcade and that’s because the devs choose to use tanks with the best frontal armor values and aimbot accuracy (which makes the game mode near unplayable btw). The AI convoys in heli PvE are buggy because the maps are absolutely massive, and the pathfinding nodes don’t match the terrain in some places. AI planes crash cus they’re just kinda dumb.
They don’t need to build a tech tree around it. They could just make the weapons/cosmetics match the BR and give the appropriate vehicles the option to spawn with them. They’d be more like modifications and weapon loadouts for vehicles rather than an entirely new tech tree.