Why not take him then? Why ask for him now? All I can think is hat he knows something that might be of use to us, or detrimental to them.

[It doesn't make sense. Three months, and no indication whatsoever that they wanted Bil back. The notice was abrupt. No lead up to it. No mention from anyone that worked with them during the missions that Bil was missed or needed in any way, shape, or form.]

There isn't anywhere that is truly safe for him in the enclosure, only safer where he is now. The tunnels or Dome are the only places that would prevent anything supernatural from harming him. They are also the more obvious places where he might be hidden. He'll need somewhere stable, secret, and well guarded.

I honestly cannot think of anywhere at the moment.