I’ve been working on articulating properly what my stances are on certain subjects, and I figured I’d go back and try to make more clear some of the issues inherent in the amiibo metagame, as well as to provide a more coherent take on the subject. This has not been edited by my junior editor Corey (we normally publish as one voice though I make mention of him occasionally just to bug him), so everything here is my own hand.
One of the traditions of the amiibo scene is the very, very conservative stagelist. Amiibo are not as smart as human players are, so certain stages that present the possibility of unjust KOs tend to be banned completely: Town and City, while perfectly legal in competitive play, is banned in nearly every amiibo tournament. This is reasonable, as there are points in the stage transitions where the platforms can cause an early demise.
However, the rules have become too conservative. Instead of only keeping tournament legal stages with no danger of early death (such as Battlefield or Smashville), the stagelist became Ω-stages only. This presents two large problems: Ω-stages are not all the same, and they are also unfair to certain characters. In fact, Ω-stages are so different from each other that the competitive scene has only allowed three of them to be used as counterpicks, according to the official rules.
Aside from the issues with Ω-stage variation, anyone familiar with a competitive Smash game can see what problems extend from only having flat stages: projectiles and long attacks have an overwhelming advantage over short but powerful attacks. In addition, the first amiibo in the air immediately has a disadvantage. Once the opponent is launched into the air, it doesn’t take a smart amiibo to realize that they should hit them again, a la Link’s up smash. The competitor on the ground can keep hitting them up ad infinitum, until their opponent dies. Having only flat stages and encouraging players to stay on the ground is a closed system with only positive feedback.
This is not to argue that amiibo would significantly improve if they were taught to use aerial attacks, or that we should go back to teaching them combos that they’ll never properly learn. An ideal amiibo like that doesn’t exist, to my knowledge. Instead, we should reconcile the idealistic stage choices with the real imperfections of amiibo AI.
It appears to me that most if not all amiibo have some sort of preferred aerial attack that simply can’t be permanently scrubbed out through training: I confirmed this in my observations of Reverse-Fed amiibo, especially my Roy (although I’ve observed this behavior in well-trained but not Reverse-Fed amiibo). Even now, when I give him a negative Speed stat and the proper bonus effects, he uses his short-hop and forward air in succession. I have observed similar hardcoded behaviors with other amiibo, including Ganondorf, Kirby, Meta Knight and several others (I haven’t tested every amiibo in this manner), so it appears that most if not all amiibo have an aerial attack coded to their AI in some way.
Now that we’ve established that amiibo will always jump, and the stages punish jumpers with hard disadvantages, what’s the logical conclusion of the metagame? Well, and this is a low-resolution conclusion but still a reasonable one: ground-based amiibo win, and the most optimal training methods are the ones that keep amiibo from jumping. This is self-evident, given these presuppositions. Just peep at the Cloud Nine customs tier list if you prefer to see my propositions proven.

Take a look at S tier. Marth and Lucina’s Dancing Blade does a lot of damage and can launch opponents into the air, and Marthcina have tilts to keep them up. Their forward smashes and counter-attacks are horizontal moves, making them useful against opponents on the ground.
Bowser’s Flying Slam is effective only from the ground, but deals a tremendous amount of damage and knockback. In addition, his tilts and smash attacks are absurdly helpful against grounded opponents, but they’re not very useful in general against air-based opponents. Bowsers tend to wait until their opponent gets near the ground before he attacks.
Link’s up smash and forward smash are one of the most effective KO options for amiibo. His forward smash deals tremendous damage and can KO foes with ease, and his up smash deals tremendous damage, launches foes into the air and also has hitboxes to the side, so as to catch opponents on the ground next to him. It’s not unusual on flat stages to see a Link use his up smash repeatedly to catch an opponent coming down from above him. The opponent has no platforms, so he must get hit over and over until he dies.
Ganondorf, the “Ganon Cannon”, has a highly effective ground-based moveset. His Wizard’s Foot is a long attack capable of KOing at high percentages, and his smash attacks gather up a copious amount of kills. Flame Choke followed by a down tilt is an easy combo for the Cannon to learn, and it’s difficult for amiibo to learn to avoid without jumping over it, which would put them at a disadvantage anyway.
Cloud, having already been nerfed, is a character built for shield breaks and damage building. His forward smash crushes any chance at blocking an attack, and his jab is almost the best in the game when facing an enemy with weight or high Defense. His projectile travels across the ground and itself can KO with Limit Break.
Little Mac… shouldn’t need an explanation.
Each of these characters are exceptional on the ground, but their AI doesn’t normally handle the air very well. Link and Ganondorf tend to handle the best in an aerial situation, and some of the amiibo in the A+ and A tiers do well in the air as well, but they never get the chance to shine and interrupt the metagame. Stages with absolutely no platforms mean that ground-based combat becomes the only combat, which causes a metagame to stale out pre-emptively.
I’m not saying that the S tier of this tier list is unjustified, because these amiibo are all highly functional. I’m also not saying that the amiibo metagame will stale out if changes aren’t made soon: I think Reverse Feeding could upset the metagames in ways that will take months to play out. My fundamental proposition here is that having Ω-stages alone, or not having enough variety in stages, is unfair to certain characters and advantageous to others, specifically the S tier amiibo.
I propose that we take small advantage of the very wide stagelist when Ultimate takes over the scene. While the actual legal stagelist is still under heavy debate, we should start with a larger selection than what we had in Smash 4. The first match of each set should be played on Smashville, to blend the platformed and non-platformed styles of play. The second match should be chosen randomly between Final Destination and Battlefield, and the third match should be played on whichever stage was not chosen in the second. This would create a more balanced metagame with less focus on the ground.
In summary, having a small stagelist is a useful thing, but the current stagelist is too small. The stages that are on it are both nonuniform and unfair to some characters. To solve this, we should expand the stagelist once Ultimate releases, so as to create a more fair metagame.