Ramming speed is the sort of poop Kathryn insisted was too uncertain in Caretaker, which is why she was marooned in the first place. She couldn't just assume victory form the other side of the galaxy or Hell. Despite her best efforts,ramming Annorax's weapon his ship might have, or there might have been temporally shield lifepods, that inthe next universe Annorax could have just started things from the beginning all over again.
So Violet.phoenix, if you had a bad week, you wouldn't mind being murdered and replaced by a doppleganger from an alternate timeline if they could be steered away from that bad week? Sure it's been a bad week, bit when you go to heaven, how many Temporal dopplengers of you are you willing to share it with?
Deepspacewine? Resetting the timeline would have led to a %100 restoration to the Jrenim Empire. To hold all those worlds, and be in charge, they would have been bastards to a degree, but then they would be held in check by their own laws and fair conduct to their slave worlds and allies.