It would be nice if the envelopments moved as part of your ship, or at least stayed with you over suns and such. It would also be nice if they blocked sun damage. Also, slaves seem to always spawn envelopments when they can, is there any way that can be stopped? Since they probably won't be able to really effectively use them anyway...

Envelopments are mostly useful for Seers and Snipers, who can fit into them. Speed Demons can use them, but they move too fast with too much agility. And I think it is fine to limit it to those uses.

And my slaves use their envelopments with quite success. I guess it is a bit down to what you are up against tho. But I've had my slaves using envelopments to block off sniper shots several times, and I don't think I would be bothered if they used envelopments constantly as I am under the impression that the device is not eating too much energy.