SMN= the active Egi Turns to the more original design of the primal, not as big, but i think you get the picture, and performs their ultimate or a more compliant version of it
I was just mentioning this idea to my wife, I was thinking when the Summoner/Scholar Limit Breaks, whatever Egi/Faerie they have out has an Attack Mode and Temporary "Flash/Old School Summons" Appearance of their Primal, and then the attack is based on that Primals' Notorious Attack Form. It is also possible that there are up to 3 attack forms per egi, if it isn't too much trouble, when you think about it, Normal, Hard, and Extreme Mode Titan for instance.

Also thinking if you have Ramuh, Leviathan, and Shiva as future Summons, this might work well. Many, many people while recognizing the importance of the Egi Storyline, still want Big Summons once in a while doing awesome attacks.