I believe it'll return.
I had an idea a long time ago that we may be able to customize already made stages, ie. editing Coliseum by adding platforms, potentially making them tourney legal as well.
As for actual approval of being tourney legal, we can have a community official "edited stage list"
Stages like Wily's Castle may have specific options to themselves. On the bottom right of the screen would be the "special" bar where an on/off switch for platforms and the Yellow Devil. On the top right, would be the basic bar, where various platforms and miscellaneous hazards would appear. These applications would match the stage just as they did in Brawl. At the same time, stages themselves can be moved to feel different from others. Increasing the ceiling distance or lowering it and a potential new mechanic to the game, making right or left blastzones smaller or larger than the other.
However, if these ideas come to fruition, I'm not sure if we would have full control over some stages like editing out walk-offs. Coliseum and Boxing Ring may be limited to their FD forms.
This is not to say I care about competitive play only. Just putting this here just in case.