I was thinking if you created a HU version of rush poker, you could limit the player pool to 4, 6 or even 8 players. I think it would be a fun way to run HU tournaments with more than 2 people, without having the wait of shootouts.
the only problem I see with it is that rush is designed to make games faster, when HU is already fast. As soon as you fold (or villain folds), the next hand is dealt. I think it would create a fun environment though - you would have to keep tabs on more than 1 villain in a HU scenario.