Alright. So I guess I should address a few things here to clarify issues.
1) Make sure to get and use "cachegen.py" for every time you add a new file into the "saltysd\smash\" file path. In general loading is muh faster. Is it the natural game's speed? No, but faster than without the cachegen.
2) Replacing the low poly with high poly files crashes the game. Maybe it will work on a New 3DS? I have yet to go in depth with testing that.
*3) If anyone can let me know if replacing the voice and/or sound effects for Bowser's uptaunt and downtaunt works. I've tried multiple times and only the sidetaunt loads any sound changes.
4) You can replace certain characters with others. For the best effect, Marth x Lucina, Mario x Dr. Mario, Luigi x Mario, Fox x Falco (maybe), Lucas x Ness (maybe). No freezes, and looks the best. I've only tried the former. Lucin over Kamui only works in game. She crashes the game after you return from training or loading the result screen.
5) Rebirth will never be an editor/obj importer. It is soley a viewer/exporter.
6) I suggest looking at the animations in Rebirth to get a better sense of where to replace the voices for Appeals (Taunts) and Wins (Victory animations). Usually it's Appeal01 (up taunt) Appeal02 (side taunts) Appeal03 (down taunt). I personally believe the Wins format varies. Attack01 is usually the jab. Never tried changing it for someone without a sound for a jab.
Anyway, that's about it for now. As for current projects
Characters:
Brawl Falcon: Done
Modern DK: Nearly finished
Dark Bowser: Nearly finished
Dark Sheik: Done
DS Era Sonic: Done
Shiny Charizard: Done
A few more, but I'll show them later
Voices:
Jason Griffith Sonic: About 90%
Brawl Fox: About 50%
Melee Dr. Mario: About 45%
B.I.S Bowser: About 70%
Melee Ganon: About 60%
Brawl Falco: 0% XD