Is there any (acceptable) way to cause a wx.ProgressDialog to be started and updated from a user driver? If not, is there an acceptable way to call and manage the wuxi/common implementation?

No, you don't get to do any UI stuff from the drivers. That's (intentionally) core to the design of CHIRP, and it is what enabled the full rewrite of the UI when pygtk abandoned us without having to touch a single driver.

--Dan