If you're talking about replacing one character with another, it's going to take a whole lot of work to do so. The only thing that will stop this from happening, however, is our current inability to edit the number of groups/entries/variables in the .bin files. It's pretty unlikely that will change, considering our current situation.
What do you mean move him to another character? Like replace someone with sonic so someone can take sonic's slot? Put sonic's model on another character's skeleton, or vice versa? Depending on what you want it might be possible.
Also, I'm gonna keep modding this game, so not completely dead XD
As for swapping sonic, if you're talking about animations and moves use PACKMANAGER and FITX to swap the moves.
As for if the game is dead... I'm still going to be modding it but as far as I know, not a whole lot of other people will be. Maybe JA or Vishera will stay behind, but overall I'd say it's going downhill.