At the risk of being a Debbie Downer, I honestly would not be surprised if experimental matches conducted outside a tournament were disregarded because...they weren't in a tournament. Which presents a Catch-22.
This is my pessimism showing through mostly.
No, this is VERY much a truth. This is why I went to such lengths to previously test out the other stages, so we had real proof they were not a problem (or were) before moving on.
If people want a walk off tournament, I can host a tournament with a few walkoffs alongside a stage or two I want to test. I want to make sure we'll have some guaranteed entry though as most of the stages we really have left on the plate to look at are stage most people definitely do not think have a real shot.
Boxing Ring
Prism Tower
N's Castle
Gerudo Valley
Gaur Plains
Paper Mario (T1)
Living Room
Green Hill Zone
Distant Planet
Golden Plains
Dream Land
Flatzone 2
These are rough estimates and some of them were really close.
Well I crossed out anything where the walkoff was only temporary, stages that had other issues (checkpoint camping, the coins giving you special stuff, etc.), the stages that were not pure walkoffs (since we wanna test how those will work for Wii U) and the stages where the blast zones were just much too close.
This leaves us with only Living Room and Boxing Ring. Boxing Ring has other issues too, which kinda make Living Room the only choice. It and Coliseum aren't too horribly different in size (yeah Living Room is probably a bit bigger but still) so it's probably the best chance there is to test these.
The stages on my list for singles testing would include
Tortimer's Island (basically by popular request, the stage is kinda big and would do better in doubles)
Unova Pokemon League (this stage is so borderline for legality in a very open ruleset)
Gaur Plains (also by popular request basically)
3D Land (by popular request)
A Walk Off Stage (Probably Living Room, strictly to test out walk offs)
The other stages while some people wanted them just aren't going to make it. So far the reddit community has done a lot and accepted more stages then I really expected in all honesty, but even then a lot of them aren't getting played on much. I mean I'm all for larger stagelists but I'm not sure I want to add any other stages if they actually cause legitimate issues when I have to fight to keep the few I have legal every week.
However I love to test things and get data. So if people think that those stages deserve a shot, I'll do it.