A possible question is, did Varic truly act for Romulus, or did he act on his own initiative? In the short run, the Senate should be less likely to oppose Romulus, which is in his favor. But in the longer run, murders like these tend to gel together the opposition. Rome has seen its fair share of Emperors overthrown once the opposition became too strong, no matter how ruthless or bloodthirsty the Emperor in question was.
So, is Romulus just so short-sighted that he doesn't realize he's sowing the seeds of the whirlwind, or is Varic already plotting against him? I think that Varic feels confident that he can remain the power behind the throne, regardless of who occupies that throne. He'll do whatever suits him best, such as killing an influential Senator with great wealth. Varic will get at least part of the money and Romulus will get to deal with the backlash. Possibly resulting in more opportunities for Varic to dispose of some enemies, acquire some more wealth for himself, until eventually Romulus will fall, having outraged his opponents one time too many.
Romulus is way out of his depth here and, barring some amazing and speedy military victories, he can't last much longer. Or can he?
PS: Mett, in my last post, I was wondering how old the Imperator, Romulus Augustulus is. Seeing as he still seems stuck in petulant teenager mode... Though it's of course nice to get a more precise idea for Remus, as well.