Still doesn't work very nicely, though. Serge is clearly identified as the point on which the future pivots. The series is fairly big on conscious, intentional action changing the future; Serge's mere survival splitting the dimensions doesn't include an action on his part. It would be more prudent, then, to say that Kid is the Assassin of Time, not Serge, as she is the one who would travel back in time, splitting the dimensions, and restoring the dead-future.
Technically, Armageddon branch does indeed work, and it works very nicely. But thematically it’s contradictory.