I just wanted to point to the recently released Avatar Legends an an excellent example of how to execute this concept, although I don’t know whether you’ve started planning Remix Rivals or not.
With Support Characters, each character in Avatar is actually 3 characters, each of which focuses on a different aspect of that character’s moves and mechanics. Even though they almost all have access to the same moves and mechanics, these change in subtle or not-so-subtle ways depending on your Support Character. Maybe you like Sokka’s sword, or his boomerang, or his El Fuerte-esque RSF loops. There’s a Support Character for each of these playstyles, even though he’s still fundamentally Sokka.
What I love about RoA2 is that most characters’ are very mechanically complex, which lends itself to diverse forms of skill expression at all skill levels. It took me hundreds of hours to find a Kragg player who was building Rube-Goldberg machines with his rock and pillar. He was doing things I’d never seen other Kragg players do, and he was only platinum. I’d love if Remix Rivals lent themselves to this type of skill expression by rebalancing characters moves and mechanics in a way similar to Support Characters, allowing players to focus on the aspects of existing character frameworks that they find most fun and creative.
I’m aware that we’re only getting a limited number of Remix Rivals, so this is simply a suggestion regarding inspiration. I look forward to the team’s spin on this concept, as Echo Fighters were such a wasted opportunity in Smash.