Dear Shachar,
Thanks for this clean and convincing model.
As for printer drivers, and services at large - there is a major question here of whether we wish Wine services to be able to server non-wine processes. If the answer is "yes", as is probably the case with an Adobe PDF printer driver, or with a winmodem's driver, root must install them.
You mean Administrator here, right? I still think Administrator != root. If e.g. CUPS passes PDF data to a wine printer driver acting as a filter, I don't see why this filter would need to run as root. The winmodem is different because it requires hardware access.
If the answer is "no", then there is no breaking of the model. With the directory structure as defined today, each user can install it, claiming full admin rights over the loca directory structure. Of course, the new adobe's printer driver only serves his programs.
Yes, both approaches can actually coexist on the same machine. Great! Now someone just needs to start implementing security handling in Wine...
Martin