I haven't tried it, but you could try killing Halsin and then ask Withers to watch over him. This I think should remove him from the party, leaving only a glowing ball at camp. At least in theory, before the patches Laezel had a tendency to raise from the dead for her cutscenes. laugh

Should work for everyone except Gale, whose game over mechanics didn't seem to take into account where his body was left. Or maybe they have patched this.