Adding a character is impossible. Brawl is made that it can only have a certain number of characters. All the playable characters, Giga-Bowser, Warioman and the Alloys. No other character slots can be made.
Wait what no.
Phantom Wings (a guy on Smash Boards, also the guy who made the FPC) has been experimenting with it for a while, and succeeded in creating an alternate character slot for Link so he could do Link vs. Zero. Sadly, the game froze when he performed certain actions, and he still has a lot of work to do. So it's not impossible, just extremely hard to do and impractical until PW releases his findings.
there we go, thats what i wanted to hear out of this post, cant wait for that day, thats what i was thinking, using code to assign a PSA to 1 texture of a character, rather than a whole character. however, once this gets done, sd card are gonna be a lot fuller, someone should make it so you can use an sd card bigger than 3 GB.
i dont like smashboards, cant u just give the link to something on smashboards when u mention it?