This is precisely what MLLE's ctrl key is for, particularly in combination with flood fill, yes. Though that won't be able to detect separated wall areas, so you have to hunt them down individually, but a whole lot of manual randomization time still gets saved for you.

That said, there's also some appeal to making AngelScript do it for you instead, since that way you don't need to worry about remembering to do randomization every time you add a new wall or whatever to the level. Just fill in all the walls with your standard tile and let them be randomized at runtime.

In any case, you're still doing a lot more work in that example picture than you need to. What I do (among other things) in violetmaze5.j2as is construct walls entirely out of single tiles, and then the script not only randomizes the individual wall tiles, but also figures out whether they're floors, ceilings, etc. That's really all you need in simple tilesets like Diamondus, Carrotus, or Castle. So instead of

, I prefer