Who is like unto the Emperor? Who is able to make war with him?
FOR THOSE ABOUT TO ROCK
WE SALUTE YOU
Anyway, looks like this is the end of the line. B's an obviously bad idea; once the Swarmlord drops, nothing will stand between the Emperor and his ascension. We could theoretically back him up, but that would involve getting to Terra without dying horribly, and then helping kill a C'tan (how?). Swarmbro's on his own, I think.
D feels like it's probably the second best option: we take out Him On Terra (and, incidentally, Terra). We'll probably neutralize the necrons, too. Though it sounds like side effects may include cutting all mankind off from the Warp and maybe killing them. Still, they'll die for the Emperor. Sort of.
A and C are both riskier but offer a chance at a less qualified victory. I don't really like C--it takes precious time, and I'm not sure whether VD can pull his deus ex machina shit while the Swarmlord's warp shadow is on Terra. On the other hand, Ahriman's never been wrong before, the details of the titan are promising, and if we manage to pull it off quickly enough, we can take out Mars.
I like A; it seems like it's got a good chance of taking out the Necron fleet. If we get a clean shot at the Noctis Labyrinth, we can stop the Emperor's apotheosis and maybe even kill him when his Bifrost bridge equivalent shatters. Feels like a trap, though. VD could hijack our gun, or we might misgauge the energy that will be reflected and obliterate ourselves, or . . .
Tentative vote for
C, I guess, although I could be swayed by a persuasive argument.