- Mario Kart series
Way long overdue.
- Paper Mario: The Thousand-Year Door
Eldin Bridge's shape with hazard extravaganza.
Any new area
from DKC2 or Tropical Freeze
Really, any location that isn't a jungle would be welcome, especially if it comes from those games.
- Metroid Prime 3
With how unfairly omitted Metroid Prime 3's representation was in Smash 4, this stage would be a great way to recover this fault, not to mention Steamlord hazard and stuff.
Sector 6 (NOC)
- Metroid Fusion
This would be the new "Temple" of Smash, as to know an unexpected stage from a less relevant but cult game.
Not to mention both the look and hazard potential (like destructible elements and X viruses) would constitute a great breath of fresh air for a series which mostly consisted of lava-themed places stage-wise.
- Kid Icarus: Uprising
I know it would be the third time
Uprising would be repped stage-wise, but I don't really care, this location has lots of potential to be a cool stage.
- Xenoblade Chronicles X
Rather than "lol all Mira Delfino-style", I would just want this place from Xeno X, as it easily has one of the most unique aesthetics in gaming.
It would be also interesting to see a certain gigantic boss from the original game, which appeared there, appearing as an hazard as well.
After Wrecking Crew, Pilotwings and such, it's time for another classic retro title which can hardly have playable representation to shine.