"The first interesting tidbit he dropped during his talk was that the final character roster was essentially completed when the design document was finalized on July 7, 2005. That was, the character list was done 2½ years before the game was completed. Sakurai said the reasoning behind this was that he knew making additions later during development would be very difficult.
To prevent this master plan from becoming a problem in the long run, Sakurai's design was constructed with the goal of trying to include as much of it as possible within the allotted time. In that way, late cuts could be made without sacrificing the production schedule. The only exception to this plan was the late addition of Sonic."
https://www.nintendoworldreport.com/news/15390
From this, we gather that the final roster was decided on July 7, 2005, with the exception of Sonic, who was added in 2007. Also, a number of characters from the originally-planned roster had to be cut. Most likely…
\RSBJ01\effect\fighter\ef_dixie.pac
\RSBJ01\effect\fighter\ef_dr_mario.pac
\RSBJ01\effect\fighter\ef_mewtwo.pac
\RSBJ01\effect\fighter\ef_pra_mai.pac
\RSBJ01\effect\fighter\ef_roy.pac
\RSBJ01\effect\fighter\ef_toon_sheik.pac
\RSBJ01\effect\fighter\ef_toon_zelda.pac
http://www.smashboards.com/showthread.php?t=137696
The list of cut characters is supported by the following passage from Famitsu, where Sakurai confirms that Diddy Kong was originally meant to be paired with Dixie Kong:
"In the latest Famitsu […] Sakurai is interviewed specifically about the newcomers […] and mentioned that originally Diddy Kong and Dixie Kong were meant to be a pair character that tagged between each other, but the plan was changed due to difficulties encountered."
http://www.smashboards.com/showthread.php?t=144627
Regarding "pra_mai," there has been speculation that it might stand for "all characters," but this is entirely implausible. In the history of the Japanese language, nobody has ever used "pra mai" to refer to anything of the sort. Seriously. Regardless, the shorthand form of player would be "purei," or "prei." Not "pra." There's absolutely NOTHING credible about the idea of "pra_mai" translating to "all characters." It just doesn't make sense to anybody who speaks Japanese. Young Link and Pichu are the only missing Melee characters from the list, but Toon Link serves as a successor to Young Link. Plusle & Minun (pra_mai) would make a ton of sense as Pichu's replacement.
With all of that said, here is what I now believe the character selection screen was meant to look like had Sakurai's original plans come to fruition:
http://i54.tinypic.com/330r9kj.png
The first half of the columns constitute Nintendo's "Big Three" (Mario, Pokémon, and Zelda), and the second half contains the remaining characters.
To prevent this master plan from becoming a problem in the long run, Sakurai's design was constructed with the goal of trying to include as much of it as possible within the allotted time. In that way, late cuts could be made without sacrificing the production schedule. The only exception to this plan was the late addition of Sonic."
https://www.nintendoworldreport.com/news/15390
From this, we gather that the final roster was decided on July 7, 2005, with the exception of Sonic, who was added in 2007. Also, a number of characters from the originally-planned roster had to be cut. Most likely…
\RSBJ01\effect\fighter\ef_dixie.pac
\RSBJ01\effect\fighter\ef_dr_mario.pac
\RSBJ01\effect\fighter\ef_mewtwo.pac
\RSBJ01\effect\fighter\ef_pra_mai.pac
\RSBJ01\effect\fighter\ef_roy.pac
\RSBJ01\effect\fighter\ef_toon_sheik.pac
\RSBJ01\effect\fighter\ef_toon_zelda.pac
http://www.smashboards.com/showthread.php?t=137696
The list of cut characters is supported by the following passage from Famitsu, where Sakurai confirms that Diddy Kong was originally meant to be paired with Dixie Kong:
"In the latest Famitsu […] Sakurai is interviewed specifically about the newcomers […] and mentioned that originally Diddy Kong and Dixie Kong were meant to be a pair character that tagged between each other, but the plan was changed due to difficulties encountered."
http://www.smashboards.com/showthread.php?t=144627
Regarding "pra_mai," there has been speculation that it might stand for "all characters," but this is entirely implausible. In the history of the Japanese language, nobody has ever used "pra mai" to refer to anything of the sort. Seriously. Regardless, the shorthand form of player would be "purei," or "prei." Not "pra." There's absolutely NOTHING credible about the idea of "pra_mai" translating to "all characters." It just doesn't make sense to anybody who speaks Japanese. Young Link and Pichu are the only missing Melee characters from the list, but Toon Link serves as a successor to Young Link. Plusle & Minun (pra_mai) would make a ton of sense as Pichu's replacement.
With all of that said, here is what I now believe the character selection screen was meant to look like had Sakurai's original plans come to fruition:
http://i54.tinypic.com/330r9kj.png
The first half of the columns constitute Nintendo's "Big Three" (Mario, Pokémon, and Zelda), and the second half contains the remaining characters.