I've watched a few episodes of Star Wars: Rebels. I find it entertaining and clever at times, and they seem to try to stick a lot of easter eggs for long time SW fans to look for.
Anyway, I was watching the show and a crazy random idea for a mash-up crossed my mind: super heroes in SW! I mean, it's not too much of a jump, since Disney owns both SW and Marvel. And it's not tooo crazy; a recent Star Wars novel introduced "death troopers"; stormtroopers infected with a zombie virus. So they've mixed horror with Star wars, why not Super Heroes?

So, here's my idea so far; it's defaulted in my brain to the show's characters, but could be changed to other people in the Time Frame from right after Episode 3 until right before Episode 6. Also the super heroes for the setting are all mostly super soldier, mutant and tech based heroes from one specific planet/species.

Rebel forces find out the Empire has made contact with a new species on a far flung outer rim world. Arriving to investigate, they discover that the world is fairly primitive compared to Galactic standards ( I see it as what we might call 'near future' level technology), but quite resource rich. The aliens that live there are fairly human (different skin tone or forehead/ears, but nothing major) and have a culture while similar to the galaxy at large (family groups, corporations, money, stuff like that), is different in many regards (no force users or history of the force; no contact with the outside galaxy). Even more puzzling is that these relatively primitive beings have found ways to enhance their bodies, giving them amazing abilities and powers! (force users will fear it's Sith Alchemy, but be surprised that it's a completely different, non evil based science)

The Rebels will want to try to help these people, knowing that the Empire will simply conquer these people and take what they want. Their attempts to attack the Imperials conducting the "first contact" mission with the leader of this new planet will be thwarted by a group of Super Humans trying to SAVE said Imperials.
After an obligatory "hero fight", the truth about the situation is revealed: This planet was conquered by it's worse villain (think Dr. Doom, Magneto or Red Skull) years ago and this group is one of the last groups of heroes left standing. They know their nemesis is planning on betraying the Empire (who they think is must be at least better than him; after all they SAY they are for peace and protecting the galaxy), and they assumed the Rebels were part of a plot to assassinate the Imperial Delegation without raising suspicion. Alliances are made plans are created to try to save a world from TWO evils.

Meanwhile, those same two evils are starting to grate on each other, as both sides plan to kill and conquer the other. Eventually all the good guys show up, and the real fight begins.

Now, I know leaving this world floating around brings some serious issues. If the Dr. Doom baddie or the Heroes drive off the Imperials, then the Imperials will just nuke the place from orbit (only way to be sure). If the Imperials stay, then the Heroes have that over their head; they failed to save a whole world that just got a little more oppressed. And you don't want your Star Wars campaign/ fan fiction too littered with super heroes.
So, the best solution is that the baddie on the planet has some device that basically takes the planet out of the picture. Not blowing it up, but maybe cutting it off from the rest of the galaxy. Some kind of hyperspace null zone, or maybe the whole star system is shifted to some other dimension. That way, there's room for them to return if someone wants it, but no one destroyed a planet (unless you want that level of story drama, at which case activate the Alpha-Omega Bomb).

Thoughts?