I'm under the impression that the final stagelist will end up being some combination of these six:
Final Destination, Battlefield, Pokemon Stadium 1/2, Smashville, Town and City, Kalos
I think this because 2GG's ruleset is already very close to this, and Smash naturally becomes more conservative over its lifetime. Even though Lylat is mostly fine, the community is so sick of it that they'll want to ban it anyway - that said, I think it can naturally be added in here, but this post is mainly campaigning for Yoshi's Story (and Stadium 1) as a balancing tool in this specific list. I've played a lot of games there, and it's fundamentally very different from Battlefield, but also serves a unique purpose.
Click this for blastzones/stage length/platform sizes/platform heights
Side blastzones are fairly normalised throughout the list. Of course, the size of the stage affects things too, but we can see that it's roughly (largest to smallest):
Kalos > PS1 > SV = BF = FD > T&C
For ceilings, it goes like this (largest to smallest):
T&C > BF > Kalos = SV > FD = PS1
I'd argue that Kalos is effectively bigger than BF; the 2 units of difference don't mean as much as the platforms, but yeah. Also worth noting that all of these are 190+ until FD.
Main stage sizes:
PS1 > T&C > FD = BF = Kalos > SV
PS1 is notably bigger than the rest - the "standard" size is FD/BF/Kalos with 160, and PS1 is only 16 units bigger. SV is 21 units smaller, but PS2 is a whopping 18 units bigger which is excessive imo. It would also make the side blastzones very close for a stage most people consider the most neutral. Overall PS1 is more well balanced, while still having what is effectively the lowest ceiling in the list.
However, that's the problem. Currently, if you want to go to a stage that's generally huge, you go Kalos - it has a tall ceiling with no platforms and larger than average side blastzones, making it the biggest overall stage. If you want smaller side blastzones but a higher ceiling, you can go to Town & City. If you want a smaller ceiling with bigger side blastzones, you can go to Stadium (and even then, it doesn't have a "small" ceiling, it's the same as FD's). If you want a generally small stage, you go to ... nowhere - Smashville has a alrge ceiling and standardised side blastzones now.
This is where Yoshi's Story comes in. Its ceiling is the same as FD/PS1 - which is also the same as S4 Dreamland - so it's not like people are going to die at unholy percentages off a tiny ceiling or something. The platforms make the ceiling effectively lower, but the smallness of the stage also makes the side blastzones effectively smaller as well. Again, it's not so small that it's excessive - it's only 3 units smaller than SV, which is still only 24 units smaller than FD (a lesser gap than the one between FD and PS2, a stage commonly used worldwide with few problems). More to the point, this stage helps in the banning phase - characters that prefer blastzones like Kalos no longer have a strict advantage in banning, and will may be instead inclined to ban Yoshi's Story.
The main argument against it is that it's just another triplat, but I disagree with that. I recognise people may just ignore my point here cuz I main Fox, but this stage honestly doesn't play much like Battlefield, or even Smash 4 Dreamland. The platforms are significantly higher - BF's are 24, Yoshi's are 29. This makes it much harder to move between them and the ground, and it also means that Fox can't even autocancel his Up Air onto the platforms, for example. The slant also makes them functionally higher if you're cornered, making it harder to move onto them in general. It also makes moving off them harder, as you have a longer distance to fall, and are thus more vulnerable. Additionally, the platforms stretch all the way to the ledge, meaning you can't run backwards off them following pressure - you always have to move forward if you want to run off these platforms, which changes the implications of being on one a lot. Also, despite the side plats being higher, the top plat is actually the same as S4 Dreamland, so it's not like the top one is brushing the blastzone.
With this in mind, considering that Yoshi's and T&C are the "small" stages (Yoshi's ceiling, T&C sides), I think having them both as CP is a bit much, so it may be best to move Kalos to a CP and T&C to starter. I think this is an effective list to test:
STARTER
Battlefield
Final Destination
Stadium 1
Smashville
Town & City
COUNTERPICK
Kalos
Yoshi's Story
Lylat can be slotted in as a Counterpick handily, and may end up improving health - in this list, I think two bans might be a bit too much, but one ban isn't enough. Having Lylat there gives a great excuse to have two bans, and it also means you can simply ban the "jank" stages of Yoshi's/Lylat if you
really don't like them for some reason.
There are a few problems I could foresee with Yoshi's. Some characters can't actually reach the platforms with their full hops (Ken, Incineroar etc.), ladders could end up broken there like they were in Dreamland, the slant could lead to dumb jank, and so on. However, I think it's being written off too early, and it fulfils a great purpose in the list.
Also Castle Siege is bad and is not a solution to this problem