That idea is certainly within reach. While having a volunteer ‘GM’ for each table would make for a volunteer-heavy event, if the number of players in a round are kept to a minimum, that can be spread out over the convention (say, no more than 6 groups at a time running).
You could even mix the idea of a tournament with building points. For example:
Each team fights a pre-determined villain in a pre-determined environment. Each villain has 3 ‘goals’ that can be earned, but they don’t HAVE to be earned. Also, each ‘tournament’ can be set up like a story. For example…
The tournament starts, each group of 4 players has their super hero team, but they don’t know who they’re going to fight, and where it might take them. They only know there will be potentially 3 villain combats. Every group fights the same series of fights.
At the start of every fight, the players are told what objectives they can chose to accomplish when battling the villain.
Battle #1 - Fight Baron Blade in Megalopolis (20pt)
- Have a Hero at full hit points at the end of combat (15pts)
- Defeat him after 20 rounds have passed (10pts) “Wait for it…”
- Defeat him in rooftop combat (5pts)
…on to battle #2, without the heroes being healed (surprise!)
Battle #2 - Fight the Matriarch in Atlantis (20 pts)
- Defeat the Matriarch while Pillars of Hercules is in play (15pts)
- One Hero is defeated, but the group carries on (10pts) “The Heroes Lose One of Their Own”
- Each Hero, at some point in the game, decides to discard his entire hand at the start of the round (not the last round of the game) (5pts) “Flying Blind on a Rocket Cycle”
…on to battle #3 (after a quick round of healing)
Battle #3 - Fight advanced Omnitron in Rook City
- Each round, when one player has the opportunity to play a card, he choses to play the card randomly from his hand (15pts) “Corruption at the Highest Levels”
- Something Environment-related (not a playtester, so I can only guess) (10pts)
- At least 4 drones are left when Omnitron is defeated (5pts) “His Plans were Downloaded into a Drone…”
Did all of the groups get to the end? Then perhaps you could come up with rules for super hero group vs super hero group. Is there a tie? Perhaps everyone who gets through the last villain qualifies for the ‘finale’, but how many points you earned dictates your start - perhaps you are down hit points at the finale? Less cards in your hands (or more)?
I threw some “names” out as examples, but you see where I’m going with it.
The other option is to come up with just group vs group play - easier from an organizing standpoint (no where near as many volunteers needed, people police themselves), but a definite change in the philosophy of the game. I like the idea of leaving a PvP as a possible ending battle…have the finale run at a late slot of the con, perhaps? All of the qualifying groups who come. Of course, that would require a creation of a different set of rules (rules modifications, actually).
Just some thoughts.