I totally want customizable movesets.
Imagine it for a second, instead of your "traditional" alt costumes, you get to change out pieces on a character. It would have to vary per character, of course, but the results could be phenomenal.
For instance, imagine it like this: A character like Mario? You can change his gloves, his clothing, his cape, and an "accessory" item.
Miss Dr. Mario? That's cool. Just switch his gloves, clothing, and cape to the "Dr. Mario" versions. His gloves would give you the electric smash attack as well as the pill ability, the cape changes his cape, and the clothing changes his recovery to the Dr. version.
Miss the F.L.U.D.D? No problem! Just switch out the "Mario tornado spinny item whatever" with the F.L.U.D.D! Replaces your down special.
Another example? Let's take our current, "Badass, but lacking" Link. What to change? The weapon, the tunic, and the type of item for each of his specials.
So want to skip out on the weak ol' master sword and Hylian shield? BAM! Kick ass with Biggoron's Sword. Increases the range and power of all sword-based attacks, (including his recovery), at the cost of less weight and no passive shield ability.
Oh, you like being able to survive different conditions? No problemo! Just switch to the Zora's Tunic or Goron Tunic to not drown in water or become invincible to fire, with the risk being increased vulnerabilities in other areas.
Oh, you're tired of your current weapons? Bam zam wazzle! Switch out your arrows for light/fire/ice arrows, your bombs for remote bombs/chu chu bombs, or your boomerang for a regular boomerang/whatever the heck else you can think of that is boomerang related.
So "Unbounded", you ask, "What do we do about the characters that can't change their movesets?"
I say change em anyway! Your pokemon trainer not pokemon trainer-ey enough? Allow the player to customize his set of pokemon! Your kirby not Kirby-ey enough? Customize him so that he uses the star rod with his forward B instead of the hammer! Customize his copy ability so that instead of copying the ability for his own use, he creates a weak low-level clone of the character to fight on his side temporarily!
So... yeah. I really want this to happen. I'm kinda sad that I typed this out now. There's no way in hell this would be done since they want to get the game out this decade.
Then again, Kid Icarus: Uprising....
