I was shocked to not find a thread for this. Feel free to post what you'd want to see in another Marvel RPG game (whether it's MUA3, XML3, or something else)
Here's my idea for MUA 3.
The roster would consist of characters playable in at least two previous games (MUA or XML). This would be
Beast, Black Panther, Blade, Cable, Captain America, Colossus, Cyclops, Daredevil, Deadpool, Gambit, Hulk, Human Torch, Iceman, Invisible Woman, Iron Man, Jean Grey, Juggernaut, Luke Cage, Magneto, Mr Fantastic, Ms Marvel, Nightcrawler, Professor X, Psylocke, Rogue, Sabretooth, Spider-Man, Spider Woman, Storm, The Thing, Thor, Wolverine, plus the game's main villain. 33 Characters in all. There would later be a DLC released for all platforms that includes Angel, Apocalypse, Black Widow, Dr Doom, Dr Strange, Drax, Gamora, Ghost Rider, Groot, Hawkeye, Nick Fury, Rocket Raccoon, Star Lord. 46 characters in all. The game's capacity, however, would be 100 characters. Starters would be Captain America, Cyclops, Iron Man, and Wolverine. Unlockables for the regular game would be Juggernaut, Magneto, Professor X, Sabretooth, and the game's villain.
The story would be original, with a main villain and his band of lackeys taking over the world. I don't know really what the story would be though. It wouldn't have multiple story paths though.
The character selection screen would be most similar to X-Men Legends 2, with the characters in a diamond shape and stats to the right, but with a lower camera angle. The actual character selection, however, would be done through a grid that shows each character's HUD, like in Super Smash Bros. The name of each character appears at the top when they are hovered over. Characters can have up to 10 costumes, and each one is named, like in MUA, but carries no passives. Passives are leveled up with skill points, like in XML1 and XML2. Stats can also be added with stat points, like in XML1 and XML2. Gear is also used in the game, becoming very important in higher difficulties. The panels in character selection are laid out like in XML2: Stats, Skills, Gear, Info. Characters can have as many powers as in XML2, including the Xtreme boost. The gameplay will be long enough to fill stats heavily.
The gameplay system will reimplement Xtraction points, the shop system, health packs, and the danger room (but will still feature simulator-type missions as well). The entire GUI will look more like the first three games. and less froo-frooey like MUA2.
The graphics will be super realistic. I'm not talking like what they were in MUA2. I'm talking Rise of the Tomb Raider type stuff. The characters will look like real people, but they won't look like any particular actor that's portrayed them.
The file system will be somewhat more simplified and explanatory. No more herostat or npcstat.
The PC version will have a special edition called the "master edition" that includes editing tools for the game for modding. It also gives you programs to preview files that normally couldn't be previewed, such as skins, and has a program to convert anything from the previous games.
And of course, everyone on the forums here would get early access to this game and the master edition.
Naturally, most of this stuff would probably be impossible, mostly just because of the scope of the thing. I remain hopeful for a better future however.