Can anyone make a mod that lets you take out more than 3 people for KOTOR I or II?

no

its hardcoded, sorry

edit: the closest thing you could do would be to use puppets. there are three slots for puppets, one is occupied by Remote, so that leaves two spots, you could assign some puppets to the NPCs already in your party (they can even be force users) except that the puppet and the npc you assign it too will always come together, (its exactly like bao-dur and the remote) using puppets you could have 5 NPCs in you're party, You, a regular party member with a puppet and another regular partymember with a puppet.

double edit: hmmm... someone should make a "Recruit the two Twi'lek Assassins Mod" Making one Twi'lek Assassin an NPC and the other be a puppet of the first, since they would come as a pair anyway.

only one problem they might or might not have weapons.

well, using puppets is the only work around that i know of for getting more than the standard 3 man party, as how many people can be in your party is hardcoded into the game engine and therefore not accessible. so... sorry. you may be able to equip the puppet with weapons in its utc file, however the puppet would be stuck with that weapon.