Well, they could in effect allow Summoners to call on a far lesser version of the Primals themselves. Basically the same thing that happened in XI, you didnt actually call the Gods themselves, only their Avatar's, a projection of their true might. Essentially they could do the same thing and allow the FC's to call on the actual Gods themselves (though to be fair to something like that, if the true self was called it should interrupt every lesser summoning completely.)

As Yoshida said, he doesnt want to see 20 mini-ifrits on the screen all moving around, it diminishes the grandeur of what the summons are. To create a truly FF effect for the Eikons, you have to do something BIG to get the full scale.

Otherwise, you're asking them to diminish the Primals into something you can basically carry in your pocket and diminish the scale of its overall potential greatly.

Unless my memory is wrong, XI is the only FF game in the entire series where the Primal/Eidilion/whatever were 'pets', kept on a perptual mp draining leash until they're no longer useful. In every other FF game they're called, they blow shit up, they disappear.

Ok.. what if Summoners do something different, lets say instead of summoning..they channel? Summoners become a medium for the Primals power, their sub classes being thm and cnj, so they can access both sides of the elemental spectrum, with water being their own native spells. With whichever Primal they're 'channeling' they are granted an increase potency to that type of elemental magic. So ie. Ifrit = Fire, Ramuh = Lightning, etc. With the 15min big skill being some sort of 'Mini Hellfire' or 'Mini Tidalwave', etc that's centered from the Summoner themselves, severing their ties to that Primal temporarily.