If they implemented 1 gunner max they could surely manage to do so without having to tie it to the slot, and ideally leave in the ability to get extra gunners via loadout recommendation for those who want it.
Compared to the current system of spammed recommended loadouts and occasional abuse for new players who go second gunner being simply blocked by the game from doing so would be much more welcoming and remove one of the major sources of ill will in the community.
