That's actually a theory that has been tried before!
But even in the best of circumstances they would have to be renegade Sirckarans- Ascar hated the Dark Side, in as much as he thought it existed which he didn't, so more accruately he hated Dark Siders. Actually he didn't have much time for Jedi, either...
... ok, let's try and make it clearer. Ascar is a good example of what goes on there, and Ascar was always calm and level headed and did not use his emotions. So that's a clear difference.
Long story short- no, it's not them. They are unlikely to ever turn up buecause they are conceptually very boring.
But yes, as soon as Gallagher killed, and felt that sudden irrational burst of anger about it... the foundations were being laid for this ending.
It was originally a prequel opening to the episode, yes, running in tandem with a much sorter Newhaven, but the schedule changed due to serious time differences between the tweo sides, and the fact that the Golden Serpent storyline was too good to cut short.
Gallagher does indeed have his challenges with the Dark Side. And if anyone thought that Anakin fell for being too stupid... I promise that this plot will work better.
Again, if anyone thinks that this is too similar to Star Wars... you may as well say that every time we have a sabre duel. How can we have Star Wars and not have the temptation of the Dark Side within the plot?
Hmmmm....only thing I've found yet in the Citadel hallucinations that could possibly be connected to Sienar/Brith/whoever the hell he is is the guy from Takuan's hallucinations....wasn't he referred to as a Sith Lord at one point in there?
I dunno, I'm probably way off but it's the only thing I've found so far that could be it.