i do think it's a mistake to leave behind jackie, but given they don't know where they're dropping in, a powerhouse rider servant is the more useful choice, and it's not like they can't just switch out later. but when capes are involved, the perpetual wild card is nothing to overlook, since jackie is a speedster that can turn basically invisible, can't have any details remembered about them, can trap people in basically a reality marble and has a really potent anti-female curse np. in this singularity specifically? that's really useful.