Another Twellman playoff suggestion I agree with: get to 4 teams however you want, then its a group stage with top seed at home all 3, bottom on road all three. Winner goes to cup final.
I'm totally claiming credit for that one - I've been pushing the benefits of a group stage for a while now.
Except advancing one team out of the group will necessarily create dead rubber games.
I would play the knockouts (3 hosts 6, 4 hosts 5) then go to group stage, with the higher seed hosting each game. Advance two from the groups, but have the East #1 play the West #2, and vice versa. Single game. Then the winners advance to the single game final.
Eventually, I would have four conferences of 8, and one team from each conference are drawn into four groups of four. (Or maybe top three from each conference plus four wildcards as Pot 4.) Advance two from each group, reseed them, and put the eight teams in a single-elimination bracket.