Okay so I have a combination of what I think is Possible and what I personally would like to see
FE 1/3/11/12
Marth,Caeda/Shiida,Ogma,Navarre,Tiki, Minerva?
FE 2
Alm,Celica
FE 4/5
Seliph,Leif,Sigurd
FE 6
Roy,Lilina
FE 7
Lyn,Hector,Eliwood
FE 8
Amelia,Eirika,Ephraim
FE 9/10
Ike
Micaiah,Elincia,Nephenee
FE 13
Chrom (confirmed),Lucina,Cordelia,Tharja?,Severa
FE 14
Ryoma,Xander,Takumi,Leo,Kaze
SMT # FE?
Tsubasa,Oribe
Villians
Arvis, Medeus (as a giant boss maybe IDK) Nergal, Lyon, Ashnard, Black Knight, Gangrel, Walhart, Validar, Garon, Anankos.
Now this is purely speculation of course, I think most of the roster will be lords and a few fan favorite characters. While I have only played Sacred Stones, Shadow Dragon. Awakening, and Fates. I have at least seen (or played parts of through romming) Binding Blade, Blazing Sword, Path of Radiance, Radiant Dawn, and New Mystery. I personally think the roster will be maybe about Hyrule Warriors Legends size before (if any) dlc, and typically variety would be top priority in a roster like this. Normally I wouldn't include so many sword users, but Koei Tecmo did do Gundam warriors, which had 50 or so characters that all played differently and true to their design, so possibly we could have a roster that size.