Except that, by the time 25 years have rolled out, the momentum will have been lost, a new Han dynasty might have already been installed in China and the Chinese might not want to rebel all over again to enthrone a new ruler.
...Honestly, if your response to every well-evidenced counter-argument in this thread is to not take any of them into account and continue insisting that the scenario fabricated in your mind, particularly the battle plan that'd require literally everything to go right, is plausible, then i'm sorry, but maybe the whole premise (conquering China, enthroning a Romanov as emperor, and then leaving) was ill-conceived from the start.
Obviously this scenario relies on the civil war NOT being resolved but only getting worse.
I've addressed every argument and changed the proposed TL greatly to adjust. It's not meant to be remotely plausible just not ASB, yes everything will have to go right, but so long as it's theoretically possible then that's my aim.