Favored Soul AoVs should be able to dismiss their archon 'shoulder cannon'.
The primary reason is that the archon's description says that it will only attack damaged foes.
This is patently untrue.
While using mephits to blow out torches in Inferno of the Damned, that little dude starts shooting the second they get in range.
If you can't make it passive in any way, then you should be able to get rid of it.
For that matter, all pets/summons should be dismissible same as hirelings/companions are.