So, like I stated in that Torian the Terminator thread, I'm not even at Taris or even Dromund Kas' second visit a la Act 2 on my Powertech and am sitting on 9060 affection with Mako, not knowing that having more affection with her than Torian (who I don't even have yet) could lock me out of the romance. Now, she grew on me as a character and all and I do not see myself liking Torian in the slightest and since we simply can't kill unwanted companions off for good, I must ask, am I screwed?
If not, then do I just level my Underworld Trading alt up enough to then stuff Torian's face with Rank 6 Companion Gifts, or do I just reroll my whole character? Of course, after reading how Mercs with Concussive Missile have it way easier than Powertechs against those two guards, the idea to reroll in already in my mind.
I am not sure if this information helps, but it might be related to what you are asking:
I was having trouble starting the romance arc with Vette on my warrior, and I posted on the forums ... someone told me that certain companion quests are related to which Act/Chapter you are in, for your class chain. As soon as I finished the current Chapter, a whole new bunch of stuff opened up with Vette.
So perhaps you could "quest ahead" in the class chain, start your romance with Mako, and keep her from being interested in Torian