It is simple, i'll put the steps here.. Mind, you i haven't tested this myself, i'm just looking at the folder structure and it's very logical.
What changed:
The location of the gamefiles. Nothing else, no physics updates, no bug fixes, we are still driving Race 07 v1.2.1.10. It's a major change so the game has to be started from Race 07, not from any of the expansions. In the first start after update you'll get config screen. It acts like a new install so My Docs\SimBin requires some action too.
The old address:
Steam\steamapps\[STEAM USER ID]\Race 07
The new address:
Steam\steamapps\common\Race 07
Everything after that is the same as before. So it's only one change, the STEAM USER ID changed to "common".
Customskins and player profile:
Rename the old SimBin\Race 07 folder in My Docs. Start and close the game (no need to go past config screen). This creates a new My Docs\SimBin\Race 07 folder. Copy all folders from the old renamed Race 07 to the new one (Customskins and userdata are the most important ones).. Do not copy the two txt files (sysinfo.txt and GameInstallDir.ini)
Mods and tracks:
Copy everything from your old Gamedata and UIData to the new location. Windows will ask for "Folder Replace", click "Yes to All".
End of "tutorial"
_________________________________________________________________
_____________________________________________________________________
You should not have any overwrites but some old mods does use the encrypted "virtual" data that is now visible. The old system was done so that if a physical copy of the file exists it uses that over the virtual one. But for us this should not be a concern, MMG mod doesn't use any modified original data. I'll add to this info by the way my install progresses.
This of course can have great consequences, XD and RTT should still work, haven't tested... A lot of mods will not work, all Weissbierbude, VLM and etc mod groups that used installers will install to wrong address.
Check also the Race07 forum, it most certainly has something about this subject...
I did raise concerns about security and i'm afraid we'll get a total dismantle of the public server scene if the teenwannabehackers find out how to exploit model data.. So i won't be talking about that elsewhere, i don't want to give them ideas.. All thou i do have some, have to refrain the temptation to go trolling in the publics now ..
EDIT: All data is encrypted bu that is really not a hurdle since the decrypter is easily googled..