Fox is overpowered. He has an extremely powerful pressure game and doesn't have any weaknesses which factor into his playstyle. Punishment susceptibility would have, but exceptionally safe moves and high mobility negate any such weaknesses and shine or whatever seems too useful. It has invincibility frames, is jump cancellable, hits on frame 1, and reflects projectiles. It also is capable of gimping some characters entirely on its own, from 0%. It guarantees followups or combo escapes in many situations unparalleled by the rest of the cast and should be more situational.
See how easy that was?
Inserting Fox into my original paragraph doesn't really prove anything for several reasons.
1st, You have failed to realize that Fox's weaknesses HAVE actually factored into his playstyle. Foxes must apply consistent technical skill, pressure, and unpredictability to conceal his punishment weaknesses. You probably view this as a "LOL its no different than Zelda teleporting to negate her mobility issues!"
But it is different. Fox's weaknesses encourage an emphasis on his strengths. It promotes particular playstyles over ones that could expose his weaknesses. This what makes characters like those viable in Melee interesting; when you play them, you have to learn how to correctly focus on their strengths and find a playstyle that is both comfortable for the character and yourself.
With Zelda, I don't get that sense of deep design or learning curve. Her mobility issues should be compensated by an emphasis on her other strategies, such as closing gaps and controlling space with projectiles. The teleport completely ignores this idea because IT IS a method of high mobility. As a result, it doesn't emphasize her existing strengths but lazily rounds off her game. This is why I disagree with the teleport.
2nd, Fox is the best character in SSBM. His punish game is absolutely broken and there are other characters that give more perfected examples of a weakness/strength system mentioned above such as C. Falcon, Marth, Ganon, etc.
However, I find it almost hilarious that you decided to switch out the words with Fox... almost as if you are suggesting that Zelda and Fox correspond in their level of brokeness.
However, I assume you're trying to say through your post that: "Fox is even crazier, but you aren't complaining about him!"
But that is a really poor message if you think about it. Its coming off as a justifcation for lazy, overpowered, and imbalanced design. Complaining about a character the P:M team has ABSOLUTE control over is completely reasonable. Fox being left in his imbalanced state (for the time being) is justified by fanbase interest and reference purpose. Using Fox as a shield against "Thats OP!" complaints is nothing short of an excuse to protect the poor design of other characters.
Your goal should be to make these characters a bare minimum in terms of viability (like mid tier at best) and work from there. Not buffing everything. They should also be designed in the respect of Melee characters who have strength/ weakness interactions in their playstyle. I have great faith in this project and I can see excellent design in characters like Snake and Sonic, but some of your other characters like Zelda and ROB are disappointing in their lack of apparent weaknesses.