here's a mod that i just created:
follow the link from there.
Edit note: I have removed the carth being jedi part from this mod. I will create a new one so that all of your party members will become jedi.
so far i am able to do # 2,3, and 4.
#2: ive changed carth to become a jedi guardian. however, you have to start a new game for this to be in effect i think. if you would like the other party members to be changed too, just tell me what class you want them to be.
#3: ive changed most of the party members' model and texture. included are: darth bandon, malak jedi, jawless malak, revan, yuhtura. some character might not have some of the animation.
#4: i replaced the texture of normal RED lightsaber with malak's lightsaber. im not too sure if i chose the right model though. i never really know how does malak's saber look like. it is upgradable just like normal sabers.
thats about it. if you want something to be modified, like if you want certain NPC to some character specifically, just let me know. or if something is not working. hope this helps, enjoy. getting kinda late here