I don't really understand why people want moveset swapping. It's just extra work for very little payoff. You guys hated custom moves, and this is basically the same thing except with an entire moveset and not just specials.
Well, not to mention that transformations also change character properties. E.g. Zelda > Shiek. Of course, poor balance isn't excusable. In Melee, Shiek and Zelda were supposed to be two sides of the same coin: Zelda is the slower hard-hitter, Sheik is the fast combo-starter. In initial design, Sheik was supposed to be far weaker than Zelda. There were
supposed to be trade-offs.
Keeping balance in mind, there have been notable imbalances between the characters, making transformations significantly less worthwhile. Sakurai stated that all characters are balanced in specific ways, but transformation characters were never balanced against their own counterparts. Because of these imbalances, certain character are played less than others and it makes the whole transformation gimmick pointless since
no one uses transform.
Transforming was supposed to be used as a variety tool: in one scenario I use a certain character to face the issue, in another scenario I transform to fit the oncoming threat. This is how transformations were supposed to be used, but this is not how transformations are used in reality. People pick one character, and choose to stay with that character.
Now, it has happened that the transformation would cause the player to use a character they are either no good with or are terrible at using. For me, I knew that ZSS was WAY better than regular Samus in Brawl, but I sucked at using ZSS. And that transformation is FORCED at times (such as Samus has a way to get to ZSS without a Final Smash, but the vice versa does not exist. That's poor balance).
Honestly, all transformations have been handled poorly. Either the characters in question were too far from each other in effectiveness, or there was some sort of stupid gimmick that made it more difficult for select players to enjoy that character.
[Insert End of Rant here]
Speaking of Zelda, BotW design please. She has to pull from the style of the game that Link's design is pulled from. There's no other way they can handle this. The two must remain a pair, they must match each other. As much as I love TP Zelda's design, Link has changed, Zelda should too.