Personally I think it will just come down to everyone not in the party at some point being outside of the sphere of effect of that artifact, and then being Absoluted up because of it.
My theory has been that there's one or more ways for any companion to leave the party, the most-gimme being Lae'zel taking off because I'm not focusing on her creche exclusively.
Getting Absoluted would be a great way of doing it, too. I like envisioning the howls of outrage from Astarion-lovers when he runs off because he's frustrated we won't let him use his powers, gets Absoluted (I love this term), and then you have to fight him!
