What about a stealth unit on the ground, similar to a Defiler perhaps? Just give it a stealth ability, a decent move speed and a sniper weapon. Since the main representative was a Rodian in KOTOR, you could use a Rodian model I think there are some models for them around the web somewhere.
Hi,
Just a suggestion but in my mod I have assassin heroes (minor and major) and I use a lua to give them an assassin like ability. For example, when I move this unit to a planet that has an enemy hero, a battle starts (just like corruption). If you want it I can send it to you. But after I fix the bugs in it.