maybe a solution could be to add a 'visibility mod slot' to all headgear? If this 'visibility mod slot' had no mod the headgear would be visible and if that slot was modded by the player with a made up invisibility mod then the headgear wouldn't show up. of course I've never modded so I have no clue if that would be ridiculously difficult to make or not (on a side note this could be extended to all armors so you could have some equipment not show on your character if you for example want to use synth armor pieces and think they look ugly as all hell)
