In my opinion, any voidsent is already too much. Remember, the goal of any life from there is to consume as much aether as possible, as soon as possible. Keeping one around as a "helper" doesn't seem like something that could work, and void summoners (in the vein of Amdapor Keep's cultists) don't tend to be alive for very long, even without player characters killing them off.
Edit: Also keep in mind that anything involving the void is going to be seen as highly illegal. Going all the way back to Tam-Tara, another Lambs of Dalamud dungeon, the head of the God's Quiver hires adventurers based on the possibility that they might be messing with the void. Anyone who had visibly void-like traits would likely be kill-on-sight for law enforcement types.
Edit: Also keep in mind that anything involving the void is going to be seen as highly illegal. Going all the way back to Tam-Tara, another Lambs of Dalamud dungeon, the head of the God's Quiver hires adventurers based on the possibility that they might be messing with the void. Anyone who had visibly void-like traits would likely be kill-on-sight for law enforcement types.