It would be pretty awesome if summoner actually took control of the Eikon (Isn't that what primals are called officially?) personally and gain a new action bar with some of their skills on. So the summoner would assume some meditative state, and you'd have to release the summon in order to act, although I'm not sure how this would work in dungeon situations...

Perhaps they could have 2 modes, with the full control one being more effective but more risky.

Time mage would also be pretty awesome, if they got meteor in the end and some other space/time stuff I would LOVE IT.