This is part of what I THINK and what i HOPE

Arcanist : Class as we read in the "spoler and leaked info" will summon or call Carbuncle
Most likely will have some abilities (like bloodpacts) that are defensive and offenseive. I am pretty sure we will either have a perpetual cost sytem alike... or something where once you make the summon, eikon or whatever itis called do an ability... it will do it and fade away.
Hopefully twe will have more "summons, avatars" than carby...

Summoner: The job that branches from Arcanist. Will be able to summon more "powerful beings" like hopefully Typhoon, Fenrir and Siren (we have seen this on the concept arts) and I assume the Summoner will be the only job with the ability to summon the primal a Free company has. Wheter it is by a limit break system, a special ability or something.

Any ideas?