Similar to BR and Ranked, you'd use DD teams and try work your way up the ladder similar to maddens H2H seasons, but we'd still have ranked as well.
Base WC round: Win one game out of one to advance online
Divisonal round: Win 3 games before losing 3 to advance.
Championship Series round: Win 4 games before losing 4.
WS: Win 4 games before losing 4.
I think this could be a cool mode to have both for online/offline play, It would also introduce new banners, icons, rewards, they could also still keep events, but each month have a new program for the Post season both an online and an offline program. Could also help people actually play more games rather than just quit in ranked, in this mode losing actually hurts you, rather than just rating points.