Idea: Cosmetic hats only appear for friendlies
Since a lot of the cosmetics are very conspicuous, a lot of players don't equip them. But if they could be reassured that wearing cosmetics will not affect their visibility to the enemy and instead only their allies, I think more people would actually equip them.
To simplify, your cosmetics will only appear to your allies, enemies will see the default character model with only your patches showing.
Post thoughts.