Not all summons have to be permanent pets, either.

In old school FFs with summons, you had those short(sometimes long) sequences where the summon disappears after it does its thing. Why can't we have that?
You can argue that it's just a fancier animation, but that can help a lot with facilitating a proper SMN fantasy.

Even this new Ahk Morn thing doesn't even properly fulfill the SMN fantasy because you're not actually summoning Bahamut into the physical world to perform the attack.

If I'm casting my DoTs, ruin, commanding my permanent pet to be bad ass and occasionally summoning a temporary pet that does awesome things, I'll be plenty satisfied with my SMN job.