I got this idea while hearing about the game Cuthroat Caverns (which I have not played).
The main idea is that SotM is no longer cooperative, there will be one winner. The winner will be the hero who can land the killing blow to the villain. This will be the hero that brings the trophy to the world. This game is more "Iron Man" Tony Starks personality than it is "Avengers Assemble." I understand that this is not in the spirit of the creation of the game, but I think it would be worth a spin. I can think of some scenarios developing that I will not share yet because I want to try them out.
The players could still all lose if they are all incapacitated or another villain or environment win condition happens. Any player that is incapacitated would still have their turn and could use an incapacitated power.
I have a great time playing regular games in the Google+ forum. Who would be up for trying this in that setting?
It pretty much destroys the fun out of support characters I.E. Argent Adept isn't known for his killing blows. Thus this ain't for me but hey once you try it you tell me if it was as fun as you thought it would.
As much as I hate to say it, as I generally like quirky PvP variant rules, MedicTank is right. Support characters like Argent Adept, Visionary, Legacy, and even Mister Fixer would be at a decided disadvantage, as they have no end-of-game "nova" ability, and only deal damage in small, discrete chunks. Even Tempest would be at a disadvantage, as his highest unbuffed attack is what, 7 points? (Lightning Slash with Shackles out)
Much as it'd be cool to see heroes going against one another--and it's a pretty common comics trope, see also: Civil War, Crisis on Infinite Earths, etc.--SotM just isn't currently set up that way. And when you're fighting against the intrinsic mechanics of the game, that's a battle you're never going to actually win, but just settle on.
Sure Tempest can deal at max damage 7 using Lightning Slash and Gene-Bound Shackles, but that isn't the only thing he can do on his turn. Electrical Storm will add another 3 damage and Localized Hurricane will also deal another 5 damage. That is 15 damage in a single turn, not too bad. Argent Adept is also capable of dealing 27 damage in a single turn as well. Fixer could get up to 9 damage. Legacy can do 11 damage on his turn as well.
Really the only hero who would have trouble is Visionary, as she can do 4 damage in a single turn unless she uses both her Twist the Ethers on herself to deal out 9 damage.
Edit: Also to toss in, whenever I play with others I always try to get the killing blow, because it's fun that way! Unless the environment is set-up in a way I can allow that to kill the villain as that is even more fun. Especially when the Final Wasteland is involved.
Legacy could struggle too; I think he could only manage 10 in a turn, and that's while boosting everyone else's attacks by 2 as well...
What happens if Akash'Bhuta kills herself? :P