Will Zhang Zuolin still die in 1928? If he does a power struggle could erupt between Puyi and his warlord generals. This could either result in a return to the republic, a return to the status quo, a new Han Chinese dynasty, or Puyi winning out. It'll be interesting to see if Zhang dies, and if he does, what the result will be.
Zhang Zuolin was assassinated IOTL under very specific TL circumstances, so while he might die in 1928 it won't happen under anything like OTL circumstances.
As for the power struggle it would not be between Puyi and the generals - Puyi quite simply does not have the requisite power for that. I also don't think you will have another attempt at a Republic - if a succession conflict goes off you probably have a faction holding forth Puyi as figure head and claiming to be a continuation of Zhang rule. Another might challenge the central faction, claiming they are "bad advisors to the Son of Heaven", and seek to replace them. Beyond that you probably have lesser warlords striking out on their own and one or more powerful warlords trying to make themselves Emperor.
The Republican phase will probably come to be seen as a bizarre aberration akin to that experienced under the Taiping Rebellion unless something drastic happens. The restoration of the Qing, while not necessarily securing the Qing dynasty itself has largely discredited republican rule.
What Princip and his associates knew is different from what we know today: they believed, ironically, that Franz Ferdinand was the leader of the Austrian war faction and that killing him was the only way to prevent a war.
But yeah, that's a complicated discussion with like nine separate sub-questions - and one that probably shouldn't be allowed to clutter up this thread.
I think we are broadly on the same page, at least I agree with all your statements, and you are right that it is a complicated discussion. Basically, agreed.
Jeez, I can get longwinded...