Very nice guide, Thanks. But as I've never really used blender/SCS modding tools before it's a little bit much work for me for something that's only client side.
I did wonder if it would be possible to have a local mod steering wheel that actually visibly turns?
Also you could use the "entries" in "bus_job_log" to place the new units in, and that shouldn't mess anything up as that does not seem to be used by the game currently. And that way the email still works.