Reposting an idea from the Porky support thread...
[How about for a new EarthBound/Mother2 stage], it could be an entire Winters stage? It's all such a neat area... The Lab, the Lake, Brickroad, Stonehenge... It could be like Delfino Plaza or Skyloft in terms of how the stage works. You'll start out boarding Tessie, and you'll ride around on the Lake on Tessie, and then you'll be dropped off at Stonehenge, where you fight both on the ground and on the tops of the stones, and it would loop back by fighting on Bubble Monkey's floating bubbles.
I can't really think how to efficiently incorporate Brickroad and the Lab, though...
Omega stage would just be on top of Stonehenge, I suppose.