I would absolutely buy additional costume slots for my BOFFs. Agreed, it should be account-wide, the same way additional costume slots for captains work.
Personally, I would want at least 3 slots for a duty uniform, a field uniform, and a dress uniform.
A BOFF on one of my toons has the bug too. He's got a second costume slot, but there's now way for him to "wear" it. Based on the existence of this glitch, I'm guessing that at least some of the programming to support this has already been done.
But yeah I still would like to see something like that...
I always hoped they would give the Omega/Honor Guard/Maco set away with visuals tied to the equip, so I could farm it for my BOs and had "kind" of a second clothing by activating/deactivating the visuals... but no... they didnt.
While you are at it. I have some more ideas for your list of feedback:
-enable MACO/Omega/Honor Guard sets for BOFF's when the player has unlocked them
-enable customization for the Borg science BOFF similar to the one from the C-store
-enable FED/KDF uniform options for diplomatic BOFF from opposite faction