I don't know if dffoo would ever collab although that would be good but for now i would wish we get in the game:

FF2-Minwu

FF3-Luneth come on he is the main protagonist!!!

FF4-Tellah

FF5-Dorgann Klauser(we need more to make a 6 man daddy squad)

FF6-Umaro

FF7-Ilfana,Scarlett,Red XIII,Lucrecia

FF7CC-Angeal

FF8-Kiros,Ward,Julia

FF9-Amarant,Quina

FFX-Rikku,Yunalesca(for the moc fans xd)

FFXI-Haven't played not sure maybe Altana+Tenzen

FFXII-Larsa,Reks,Rasler

FFXIII-Jihl,Lebreau(i'm still doing work for moc fans no worries guys)

FFXIV-Another one i haven't played but i would say Zenos and Gaius(that one reminds me of Grahf from Xenogears that bastard was really hard to deal with) add also that girl Minfillia she looks cute.

FFXV-Lunafreya(guys you are gonna laugh a lot she has Ribrianne's voice),Regis,Somnus,Nyx,Crowe

Dream come true collab would be with Legend Of Dragoon my favorite psx game ever if it comes in the game i will have nothing to eat or stay anywhere but at least i would play with Dart hahaha.