Your idea is pretty close to the "Summon Bahamut" ability so it's not impossible.
I have the same idea actually, removing pets from the game and adding the Demi versions of the Egis instead. Maybe add Ramuh, Leviathan and Shiva too.

How they'll work is you have to rotate through them because of the long cooldown, like how Bard songs work. Some are good for single-target, some are good for AoE, and some have more useful buffs depending on the situation.
It would also be good if they get more than just Enkindle [summon] as a skill, maybe a party buff, and 2 other attacks that have a pretty short CD (like an AoE, a single-target attack, a DoT etc.). For all of this to work better though, it'll only need one DWT phase, or remove DWT entirely and incorporate the effects onto the summoning instead.

But first of all I hope they fix how Demi-Bahamut works, like how he moves around and how clunky Wyrmwave works. Otherwise, it's a step in the right direction for SMN's design.