[thejeff]

1) Yes, though it's probably not cost efficient.
Don't forget Blood sabbath works the same way as communion and is compatible with it.

2) If the slave goes first he will act every turn, if he goes after any master he will not. What he's scripted for doesn't affect this. If the master does not cast, the slaves can act.
Using thugs as communion slaves does work. If the master is also a thug, having him buff the slaves then attack will allow them to attack also. Simply making sure the slaves go first will also work. If the master is more fragile, you can have him cast the self buffs and then retreat.
Bear in mind the slaves, especially if they don't have the right paths, are likely to start fighting with a lot of fatigue.

I used this with Vampire Counts. Using one of them as a master for Soul Vortex and a fortune teller for luck and other astral buffs.