Yes, you can.
Note: Go here for further Questions
Alright,
first, download the Savegame editor by tk102 here
Extract the files into your Kotor2 folder, then start the kse_309.exe.
Then, choose the game in which you want to change mandalores' model (for example "0000002 - Game 1"). Click the cross beside it. Then go to "NPC". There, choose Mandalore. Select Apperance. A list of Models will be displayed at the right hand side. Search for "Party_NPC_Mandalore_No_Helmet", select it, then click "Chance Apperance", then "Commit changes". Now start up Kotor2 and load the save.
Hope this helps.