This will give your character a spell, this spell add the targeted Character to your party, if you cast it on a Character already in your party it will remove it(even multiplayer character) if you want to be able to recruit the character again you can remove them in your camp, they'll be teleported automatically even when changing act (at least for multiplayer characters, some random NPC wont)

There is no Party limit if you recruit with the spell but their will be if you try recruiting with the legit way

It could break the game i haven't tested it in many specific situation, i have found some bug when adding markus and isobel to your party during the kidnapping it will conclude that you help on of them then trigger the kidnapping again when leaving the camp

you could probably add Haislin and Minthara to your party at the same time with this spell but i didn't tried 

you can resurrect the NPC in your party and recruted character will join your faction so your ennemies are their enemies 

you can open freely inventory of Trader's that are added to your party or trade with them like usual excepted if you take them from an ACT to the Other.

REQUIRED
bg3 script extender 

INSTALATION:
I recommend bg3 mod manager