It would be interesting if the HP of the summon was linked to the HP of the SMN.
Meaning if the summon dies, so does the SMN... (FFIV)

Anyway, if summoning a tank style monster, then the summoner's HP might get a boost too, etc... The SMN itself could end up being the most versatile class in the game. They could be healer, tank, DD, buff/debuff... it would all depend on how they do it of course, but ether way, I'm excited for the class and can't wait to give it a try.