Crowndsourcing Part Iii Good Guys Bad Guys Or Bad Guys Who Think Theyre Good Guys

If yall remember the previous crowdsourcing RPG threads I posted earlier, you will recall that I had the idea of throwing out a general premise for a campaign I wanted to run and letting others shape the particulars. It went pretty well overall, but Im too damn lazy to link back to them.

My original idea was for the PCs to be mystical supernatural heroes, who were returning to a world devastated by nuclear war (or some other horrendous global disaster) to fix it. The problem was, magic had faded over time and thus they returned a bit too late to stop the disaster as they thought they would. The one question I have unresolved is about a tweak that someone (dont remember who- Ive slept since then) mentioned regarding the PCs. An old gaming / MU* buddy I was taking to about the crowdsourcing really loved it. I present the issue to you for one more round of crowdsourcing the campaign.

Heres the issue: what if the PCs werent heroes in the past at all, but villains? Maybe they think they were heroes, but in reality they were either being manipulated or their faction was simply the lesser of two evils. Maybe history looks back on their deeds and considers them monsters when they really werent. Maybe the Gods (tm) are giving them a chance to redeem themselves. I admit Im not at all sure how this idea would work or how to pull it off, but thats why Im posing the question here. What do yall think? Does this idea sound interesting? If so, how might I as GM fool the players into thinking their characters "were" the good guys, but in-game slowly reveal that they were not at all? And wouldnt this mean that either their traditional nemesis was either the "real" good guy, or waaaay worse than them?