What do we do with them? The ability to carry 10 just takes away too much of the danger from the missions and makes tech rezzing and moon atomisers useless, thus harming teamwork.
Now, if this game was like PSP2 or PSO2, I might suggest limiting scape dolls to a maximum of 1 at a time. I would suggest however a limit of 2 or 3 for PSU in its current state, particularly due to bullshit moments the player has no control over (enemy resync cause you to get hit by an enemy stampede multiple times, mate lag, MEGID EVERYWHERE and numerous other one-shot mechanics). However this largely depends on how difficult we're making this game, but I wouldn't suggest allowing characters to carry more than 3 myself.
If theyre dying more than that, they're either undergeared or not really skilled enough for the run. So come back later or go find a party.
I do think scape dolls should be purchaseable from NPCs still, but make them much more expensive.