MMO fans.
SE hasn't had more than 500k subs in years. That number is shrinking rapidly (2 server merges in 1 year).
They should keep certain aspects to make it a FF MMO (flexibility to change jobs, great world, story, and art direction, chocobos, airships, world in danger, etc.).
They should learn from what they've done and what everyone else has done, and produce a game that will appeal to a wide audience.
Especially since most of the better FF games are older, and almost no one holds FF13 in the same regard as FF6, FF7, etc.