Quote Originally Posted by Keyln View Post
The funny thing about lore is that it can be changed and updated to do whatever the devs want it to do.

Lore is no reason not to do something.
The problem right now are the storyline quest. They would need to redo a huge part of it, same for some cutscenes if they would like to use classic summon like Ifrit for the summoner job.

However, just check this page: http://finalfantasy.wikia.com/wiki/List_of_Summons
If you take all the summons in account there are many more that FFXIV primals. Sure the one used as primal can't be summoned but that still leave a big list of usable summons.