Looking for a specific mod
 

For Jedi outcast, I am looking for a mod where I can just spawn reborns and duke out with them.

You've already got it. It's called Jedi Outcast.

Just load a singleplayer game, use /devmap to boot a map of your choosing, spawn 'em up and knock yourself out.

Wow, sweet. Can you suggest a flat open map?

Try a map called "ladder" its a small map but it has waves of reborns and some of those dark troopers, and at the end you fight tavion and the other boss, just put it in gamedata/base

I'd suggest duel_kaminoan (aka "Kaminoan landing platform") by Khaza. It's on jk2files.