I'm just gonna spit-ball here.
While I very much enjoy the training room as is, i'm not opposed to adding features on the stage. I'm digging the ledge above the wall, though a hard platform could do the same thing without physically changing the stage. Which brings me to my next point:
A platform is a good idea, but there's an immense amount of space that everyone wants to fill in their own way and so it opens up more questions. Would the platform be closer to the wall, or the ledge? Soft or hard platform? Grabbable(?) ledge? Would it move? What directions? How high? Low? Slanted or flat? How wide or narrow? Just one platform? How many platforms? Do we copy an existing stage's layout or create a new one?
It's hard for me to picture a really good platform setup without making the stage look too sloppy or cluttered. I figured a moving platform, ala Smashville, would do the trick, but we'd all have to wait for the platform to come back and position itself ideally. MAYBE a stationary hard platform by the wall, and a stationary soft platform by the ledge. Someone mentioned having a set of platforms that is high enough to where it somewhat isolates itself from the rest of the stage, thus creating a platform-based area. I can see this turning out not unlike Battlefield or Pokemon Stadium 2, but more compact/less intrusive. This may be the most functionally thorough suggestion. As I mentioned, a ledge-grabbable hard platform along the walled side could also double as the platform to reach the training platforms.
It still sounds kinda messy though.