Nice. I look forward to reading it. I'm thinking about digging around and picking up all the Celestial Empire stories that are out there, I think the Dragon's Nine Sons had a list in the back, in lieu of a collection, which I hope to one day see (although I'd prefer a van Helsing collection, those are really great stories.
Anyway, the beauty of alternate history is that it gives you so many options, for you, the Celestial Empire is a way to tell stories in their world, for Kim Stanley Robinson The Years of Rice and Salt was an extended essay, Jo Walton's Farthing/Ha'Penny/Half A Crown are sort of in the middle ground.
Dear Lord, my comments are getting longer these days....
 

You won't get any complaints about long comments from me, Greg!

But I think you're right about alternate history, and perhaps it's even more flexible in terms of the uses to which it can be put than any other sf subgenre. Mmmm, something to think about.

But a Celestial Empire collection is inevitable at some point, rest assured. (The three Van Helsing stories are actually the first three chapters of a novel, Travel Towards the Sunrise, that I'm sure I'll get around to finishing sooner or later. And thanks for the kind words!)