In my mind, the ideal system would be a character blowout once a year where 6 characters get dropped at once alongside a balance patch, preferably after Capcpom Cup.
In the time period between Capcpom Cups, release fucktonnes of customization options, stages and improve on the UI/gameplay/etc.
MAYBE have a balance patch right after EVO, but that shouldn't be mandatory if the balance is considered decent or if the planned changes are too much.
But the problem with this approach is it requires budget and planning.