I do not have a new Via or 1000, so this is just an idea that came to mind ....
Using Myhome, I assume one can make a backup of your tt.
This backup is stored on the pc's hd in a windows readable format - right?
Now, what if you would replace the map on the backup with a newer version, and then use Myhome again to restore the backup.
Probably tomtom has thought of some clever check to stop this, but then again maybe not.