So, I am currently tempted to make one of these with one of the following gimmicks:
1) "No Marvel or DC, but everything else is up for grabs" Like, Transformers, TMNT, The Boys, Invincible, Power Rangers, Buffy The Vampire Slayer, Bananaman, Thunderbirds, Danny Phantom, Superted, Mighty Mouse, Danger Mouse, Count Duckula, Jimmy Neutron, VR Troopers, Masked Rider, Darkwing Duck, Freakazoid, Tattooed Teenage Alien Fighters From Beverly Hills, Sailor Moon, The Care Bears, G.I. Joe, Powerpuff Girls, Digimon, Captain Scarlet, Conan The Barbarian, Sonic The Hedgehog, He-Man, Stargate, go nuts.
2) Future RP. The idea is that we skip the origin stories that we get bogged down in. Everyone plays a hero who has been on the job for at LEAST 20 years. OR is playing the next line of their legacy. Damien Wayne as Batman, Old Man Logan, Jubilee's "X-People", Jonathon Kent is Superman, May-Day Parker Spidergirl, etc.
3) Hit the Shuffle Button. You pick the character you want to go with, but then the GM randomly rolls which legacy the character picks up. E.G. You apply for Bruce Wayne, he witnesses his parents get shot in front of him. He goes home and he is *Rolls the dice* Bitten by a Radioactive Spider, becoming the one and only Spider-Man of Gotham. T'Challa of Wakanda is raised to become the champion of his people. He *Rolls dice* is given the sacred ring to become the Green Lantern. Hal Jordan, he is a test pilot testing a brand new plane, when suddenly his plane malfunctions and he goes down over Nevada where *Rolls Dice* He is hit by a Nuclear Blast, irradiating him and turning him into the one and only Incredible Hulk. Steve Rogers is a guy absolutely determined to fight in WW2, but is too physically weak. That's when *Rolls dice* he learns that his parents weren't actually his parents and that he was simply found when a space-ship carrying him as a baby went down in Queens and he's really the Last Son of Krypton, after reading the message, his amazing powers are revealed to him as he becomes the one and only Superman. We can also just let people decide for themselves.
4) Silver Age. Essentially, the tone of the RP is set to "Camp" i'm talking Adam West Batman, Japanese Supaida-Man with his Megazord, the Justice League and Legion of Doom having to play Baseball to decide the fate of the world. Extra points for anyone who can reimagine gritty and super-grim-dark 80's-90's storylines like Demon In The Bottle, The Night Gwen Stacy Died, The Dark Knight Returns, Days of Futures Past, Death In The Family, Born Again, Dark Phoenix, Age of Apocalypse, Knightfall or Clone Saga in campy Silver Age style.
5) Something along the same lines as this, but just open it up to more franchises to be viable, so long as they fit the them.