On a different save (As Atletico Madrid) my B team got relegated from a Second Division B group and haven't been seen since. I signed alot of talented older guys and going by their stats (goals and goals conceded by keepers) they killed it last season, but I'm sure that doesn't matter, from what I've read, only rep matters. A day before the start of the new season I used FMRTE to edit the B team's rep to 10000 AND I changed their wage budget to be higher than their wage bill.
I start the new season and get a message saying 'Atletico B turn professional' because the club is now playing in the Spanish Third Division Group 7. I guess this means they were in a league LOWER than that and so now they've been promoted and if I do the same thing next season, they'll be in the Second Division!!!
EDIT: I also changed the chairman status to 9500, not sure if that matters.