Just an idea that stuck me on the way home, would it be feasible to make a toggle to lock a choice when setting up a game?
Like, say, if you wanted to take on Voss in Megalopolis, but wanted a randomized team. Or you have the Prime Wardens set up to go, but want to roll the dice on the environment and villain. Of you want to play with Guise but aren't particular about the rest of it.
That sort of already happens: if you make your selections first, Randomize will fill in the gaps. If you hit Randomize a second time, everything will randomize, though.
I'd like to see the reverse, blocking certain characters from showing up via randomize
I'd like to be able to set the number of heroes to randomize in multiplayer. It's not terrible, randomizing one and then picking another, but sometimes you're just up for whatever and need two heroes, y'know?
This is on our list to do in the future, but there are some ways to do it within the existing system that don't take many (or any) more clicks than a "locking" feature would.
You want to take on Voss in Megalopolis, but wanted a randomized team: Choose Voss/Megalopolis then press randomize, and the heroes will be filled out. Or if you want to choose from various teams: Press randomize as many times as you want, then replace the villain & environment.
You have the Prime Wardens set up to go, but want to roll the dice on the environment and villain: Do that with no environment and villain set up, and press randomize, and they will be filled out. Want another combo? Remove the environment and villain and press randomize again.
You want to randomize two or three heroes in multiplayer. Select any two or three heroes and press randomize, and you will get the same number of heroes randomized.
Oh snap! 
Thanks! 
I didn't realize it worked that way. Thanks for the heads up.
Maybe I'm missing something, but how is the first of these different from the second? If I have (all five) Prime Wardens set up, with no villain/environment, and hit "Randomize," the game will fill in the Villain/Environment.
But then, it says that if I select a given number of heroes (ex: five), and hit "Randomize," the game will spit out a different randomized five-hero combo.
Which is it? If I select five heroes and hit "Randomize," will the game fill in a villain/environment combo, or select a different random five heroes?
If you select five heroes and click randomize you'll a random villain/environment combo. If you don't like that combo remove the villain/environment remove them and click randomize again.
My understanding is that if the Villain/Environment slots are empty, those will be randomized, but if they are full, everything will be randomized, and the number of heroes will be equal to the number of heroes selected.
The second one only applies to multiplayer, as indicated.