Thanks for your suggestion, bogani. It’s a very interesting idea.
It is possible by replacing left (right) hand drive car's "cameras.xml" file with right (left) hand drive car's. I sometimes use this way when I want to virtually change the driver's seat to the opposite side (e.g. when I want to drive Lancer Evo. with left-hand drive etc.). And we can use the same way to create the current WRC onboard-style camera.
Here is an instruction.
(e.g.) How to create the Co-Driver's Side Camera for "Impreza WRX STI Spec C R4".
1. About "Cars & Folder Names" (which folder is which car), please refer to this thread.
http://www.racedepartment.com/threads/dirt-rally-cars-tracks-folder-names-list.104727/
2. Please make a backup of the original file.
3. Go to the following directory.
C:/Program Files (x86)/Steam/steamapps/common/DiRT Rally/cars/models/mer
And copy & paste "cameras.xml" file in it => into the following directory and overwrite the existing one.
C:/Program Files (x86)/Steam/steamapps/common/DiRT Rally/cars/models/sti
4. Run "DiRT Rally".
5. Select "Impreza WRX STI Spec C R4" (R4 Class) and switch the camera to "Head-Cam" or "Dash-Cam". (If the steps above were properly done, the camera(s) should be displayed on the right side.)
6. Then adjust the camera(s) to the desired position.
If you want to watch the replay with the adjusted camera position, please adjust the camera(s) before starting SS. Then start & finish SS, and switch to the adjusted camera during the replay.
That's it.
Here are some screenshots.
This is literally “Co-Driver’s Cam”.
In this Mod, I adjusted the center of the steering wheel of each car (not mentioned in the Readme though), here is the list of the X-Axis (left/right position) value of each car (quickly exported from my Excel data, sorry).
(Note: minus value = right-hand drive car)
This is a useful information. I'll add this tutorial in the Readme when I update the Mod next time. Of course, I won’t forget the credit to you.
Hope this helps. And thanks again for this nice suggestion.