Well... looking at the original script (KGC's website)...
http://f44.aaa.livedoor.jp/~ytomy/tkool/rpgtech/index.html
... I gathered all the 'calls' for this script.
Figured... answer 'em all first.
Calling the statement
call_partyform in a [map event], or scripting it into a system allows you to bring up a partymember switch system.
Needed one to find your answer. Heh... built in.
Calling the statement
$game_party.changeable(id[, permission]) where id is the id of your hero and permission is either true/false, is what determines if you can remove a player from your party or not.
Permission is optional if it is true.
$game_party.changeable(1,false) ... cannot remove player 1
$game_party.changeable(6)... can remove player 6 (See? true is optional)
$game_system.partyform_permit can be either true or false. It determines if the party changer (above) will be enabled.
$game_party.sort_member, when called, sorts your heroes in ID number order.
(
Note: Passing 'false' values through map events may cause the game to freeze. Stupid RUBY/RGSS thingabob. Best workaround? Make a separate RGSS script that will do the false-passing for you.)