Here's my take on each of the Online stages of Splatoon and how they would translate to a potential Smash stage. While I do think Inkopolis/Booyah Base is the obvious pick, no one knows with Sakurai. I'm also assuming no travelling stages, nor heavily modifying the stage (like taking the whole thing and putting it in a giant floating platform).
Sorry if some of these aren't very clear, it's hard to express my ideas when I only have them in my head.
Saltspray Rig: One of Splatoon's signature and most popular stages, and likely the most logical pick from the online arenas. They could do a simple stage based on the bottom section of the map, with one big platform in the middle and maybe add a couple of floating platforms on each side.
Walleye Warehouse: The other signature stage, but I don't think this one would translate as well to Smash. They could base it on the middle section of the map, but then both sides would likely end up being walk-offs.
Urchin Underpass: This stage has too many corridors and alleys which are kinda the signature of the arena, and I don't think those translate well to Smash. I guess the middle section could work in some way, but I have trouble picturing it.
Arowana Mall: I think this one might work as a low middle section with two elevations (one on each side), based on the section near the starting point.
Blackbelly Skatepark: Don't see it. Too many slopes and curves that don't translate well to Smash.
Port Mackerel: I can't think of a single way this one could work. The consecutively placed towers would translate terribly to Smash.
Kelp Dome: The section in the middle could work combined with the metallic bridges that are placed around.
Bluefin Depot: The starting section could work, acting as a higher elevation to the rest of the stage.
Moray Towers: This one is VERY interesting. The zig-zag pattern could work very well for a big stage, but some people may not like it because, you know, it would be pretty damn big.
Camp Triggerfish: I'd love to see this one, personally. It could work by having two sections, with a lake in the middle emulating the traditional "rival camps" scenario.
Flounder Heights: This one could work as a Saffron City/Fourside-type stage taking place atop the buildings.
