WARNING: MEGA WALL OF TEXT - TL;DR AT BOTTOM
In order to determine the viability of a stage, you have to consider a few things. Along with that, you have to consider some things about the stagelist as a whole.
For a single stage:
-are there aspects of the stage that cause CONSIDERABLE disadvantage for certain characters or archetypes? If so, it should not be used. If there are minor disadvantages caused, that’s kinda the point of counterpicking - to have the stage potentially help you win
-are there any parts of the stage that fundamentally affect gameplay, or cause large amounts of distraction? Some stages are too much visually (looking at you, FD), and some fundamentally cause the game to be played differently (2d stages, walkoffs, caves of life, sharking)
- if a stage has an annoying component, but not problematic, deal with it. Stages with slants are included in this, as long as the slants aren’t gamebreaking (can anyone explain the issues people have with slants? I don’t get it)
In terms of stagelist, you need:
a) a diverse set of starters that are the most neutral stages in game, that provide *slight* advantages in play style (for example, stages that lean towards heavies, campy characters, etc.)
b) enough counterpicks to enable the loser to have a slightly larger advantage due to the stage
c) enough bans to ensure the winner can remove some of worst stages, but not enough that the competitive advantage for loser is removed (ex. Should be able to remove smallest stages, but not all small stages, etc.)
d) the number of bans shouldn’t be contingent on the raw number of stages, but rather based on point c. If there are a few neutral stages, 3 large stages, and 3 small stages for example, there should not be 3 bans, even if there are 30 stages. 2 in an example like that would be reasonable, since counterpick gives slight advantage, but not to an unfair degree.
e) because of points c and d, in order to make counterpicks fair for all archetypes, one stage size/type should not have more significant differences (for example, say the average size decrease of small stages to neutral stages is 20%, but the increase for larger stages on average is 40% - this would give more advantage to those who prefer to pick large stages, which should be avoided if possible).
As for the stages themselves, this basically leaves us with the usual suspects - FD, BF, SV, Lylat, PS2, Kalos, Unova, T&C, Yoshi Brawl, Yoshi Story, Castle Seige, and I would add WW. The questions to ask are - should they be used? If so, starter or counterpick?
Stage layout variety is important for starter stages. Thus, a stage like BF with middle of the pack size is probably the safest triplat, and should be a starter.
I decided to look at all viable stage ceiling and side blastzones, and stage length. I averaged each of these to determine the middle (of course, other nonstatistical factors come into play, but more on that shortly).
Before I discuss each stage individually, here are a few points to consider:
-PS2 and WW’s average deviation from average (heh, average of side, ceiling, length all averaged together) are basically identical (within one unit). Of course, ps2 deviations have less of an outlier, but nonetheless they are practically the same.
-Lylat, according to the numbers, is the most “average” stage overall.
-Next largest deviations are yoshis story, island, seige, and kalos
-The most average stages overall are T&C, BF, Unova, FD, SV, Lylat.
Genesis 6 rules are a little concerning - if you strike SV at the start, you’ll play on stages that are all significantly larger than average, stage length wise. There’s also a significantly larger than average side blast zone from the starters. Aside from having ps2 as a counterpick (which wouldn’t be a bad idea, tbh, but no one would go for it), something needs to change.
I propose that rulesets should keep all 12 of these stages, as the variance between large and small stages is very similar (7 smaller than average side blast zones, 7 larger than average stage lengths). For starter stages, the usual stages are mostly okay (fairly average size overall, good shape variance biplats, monoplat, short triplat, triplat). I would change FD to Yoshi’s Brawl. There are a few reasons for this. First, FD serves better as a counterpick, because the same people that would ban a flat stage typically would also ban larger stages, but FD means that no matter what, all your opponent has to do is ban Lylat and SV to guarantee a large stage. Yoshis brawl adds a smaller stage, with one large platform. It also causes averages to be pretty consistent (side and length slightly above average). With this in mind, those who want small stages can get one of Lylat, yoshis brawl, or SV, while large preference can get PS2, BF (as well as Lylat and sv being average size to slightly small anyway). This puts neither competitor at a disadvantage.
Having all 12 stages is for a few reasons, but one major one is that if you average my proposed starters, and the proposed counterpicks, the average of the two is almost near average (slight adv to large in starter, slight adv to small in CP). I can post the sheet if anybody wants it.
As far as bans, 2 or 3 would potentially be viable, but to maintain options while also allowing for CP to give a slight advantage, 3 bans would be ideal. Let’s say a loser wants a small stage, winner might ban WW, Siege, and yoshis brawl. That would leave story, Lylat, and SV as smallish to average stages. Again, slight advantage to smaller stages, but nothing drastic. The threat of warioware enables successful small stage counterpicking, even if it literally is never played on; without it, all small stages can easily be banned. On the other hand, for large stage preference, if you banned biggest stages, you’d ban kalos, ps2, and unova/bf. That’d leave you with BF/Unova, FD, T&C as biggish stages - again, advantage but not too much of one. Simplified examples but I hope you get my point.
tl;dr - changes to genesis 6 ruleset - Switch FD to counterpick, yoshis brawl to starter, add Warioware, 3 bans, 12 stages total. That would balance out small vs large stages to enable more balanced starters and counterpicking. Read the wall of text for explanation - I think it makes sense