We can create a new "contact engine" for QtMobility as it is. I had to play a little bit with the "maemo5" backend and end up creating an "alternative version" of it to be able to use the latest code from the repository. I think would be pretty simple to start with the code that you created for TOR and create a QtMobility Contacts backend for google contacts.

Allowing to merge these contacts with a different engine (or the local contacts database would be a different issue all together).

Off topic:
I wonder why we still don't have a qt mobility backend based on sqllite. If we could have a "database" that would cache/aggregate contacts information from different backends it would be easier to deal with syncing/merging. I guess that is the idea with the current "contacts database" but I would prefer a cross platform implementation where we could create backends that deal with the data (sql) directly.