[Illuminated One]

I would certainly like to keep that they can fight or fire bows, but I wouldn't have to much against it if they couldn't cast spells anymore.
However being able to change the casting order has some other benefits. If you're using a crystal matrix then you want all the slaves casting communion slave before the master in order to get a defensive buff or strong spell cast on the first round.
Also if you combine some mages without a communion it would be a good way to optimize scripting.
For example when an A4 mage casts Storm and A2 mages cast Storm Power after that or a priest blesses all mages before they cast their first spell.