An idea...

[8-peacock-8]

So if there wont be an SSE type mode this time around; how about putting some of the locations from SSE as stages? It would be a good way to add more stages and competitive players will probably be happy about it. (i'm not a competitive player. So i wouldn't care that much if these stages are added or not.)

Examples:
The stage where you fight Evil Zelda/Peach as Pit or Link.
Tabuu's Arena
The ship that flies around the Island Of The Ancients.
The Arena/Pokemon stadium reskin from the beginning of SSE.
The place where you fight Bowser with King Dedede.
The locations from the Great maze where you fought those evil versions of the playable characters.
The Mountain where Lucario and Meta Knight fought.

 

[KingofPhantoms]

Tabuu's Arena would be kind of redundant with Final Destination, or the other way around.


The ship that flies around te Island of the Ancients would be cool, but also a bit redundant with Final Destination. (or maybe not, I can't recall if the ship would tilt during the game)

The Midair Stadium/Pokemon Stadium Reskin would either cause less or more trouble with Pokemon Stadium's tournament legality.

The Great Maze locations would be interesting, but theres quite a few to choose from, perhaps the platforms (including the main one) could change over time?

 

[8-peacock-8]

Another possibly good place could be the location where Diddy and Fox battled Shadow Bowser. it has platforms and crap.

 

[Oracle_Summon]

Extra stages may be welcomed, but only if they function differently or if there is a very limited amount of Subspace Emissary stages.

Personally, I would like space reserved for special events more so, than stages that come from the Subspace Emissary.

 

[N3ON]

Honestly if this were to happen, it probably would've happened with Brawl. I mean, the references would be nice and all (to those that want to be reminded of the SSE ), but honestly I think most people would probably rather just have competitively viable normal stages. The most I see is a stage that takes inspiration from an area in SSE in layout or something, but from an actual series.

 

[APC99]

The Mid-Air Stadium seems really Smash Bros. like to me. I'd enjoy it being used, maybe a stage in vein of Battlefield and Final Destination?

The Falcon Flyer would be really cool as a stage, especially if bombs hit it and it tilted like it did during the Meta Ridley fight (of course, we'd need a event match vs. Ridley here.)

Maybe one like the secret room in the jungle where it blows you upwards? The bottom would be the air blowing upwards, plus two leaves as platforms. One other leaf in the middle acts as another platform, but most fighting takes place in the air, as it pushes you upwards and slows your descent.