I have managed to unlock sabers that are used by NPC`s in SP game. If anyone is interested follow these instructions.
1) extract sabers.sab file from Assets1.pk3
2) open sabers.sab with any text editor
3) find and replace NotInMp 1 with NotInMp 0
4) save changes to file
5) add file back to assets1.pk3 or make your own .pk3 file
6) run Mp game
new sabers will be added to saber selection screen