Yes! This would make addition to (at least) the entertainer background. (Maybe if you a Bard entertainer you get perfomance proficiency at level 1).
I wonder what other background it would work for. Maybe Urchin?
Should the soldier background give a weapon proficiency, then?
That would be cool. It might be a balancing issue, but the Sanctum Stalker background already comes with a free cantrip. The cantrip kinda stinks (it’s Shadowheart’s damage cantrip - 1d8 on a dex save) but it’s not nothing.
I’d love any change that makes the backgrounds more unique and/or relevant in game.
Edit: I just booted BG3 to check the Sanctum Stalker background and saw that it went the way of the Hermit. Bring those back, you cowards!
