Perfect concept and work! Exept one thing:
i'ts troublesome to drive a modern truck with a very old interior...
Make one or two interiors for the most recent trucks (inspired by a recent Kenworth T800/T900, or the Freightliner classic Xl 2000. Two pretty good trucks, and very similar to the vanilla truck)
You can also open the sleeping cabin with the drive cabin, to make it one large cabin, like the most of american trucks.
I hope my suggestion will help you to make this mod the most complete as possible ;)
We doin' some Nam' offroading here! Amazing update as always. All am waiting for now is that Air Filter for the Base T-Series. And how about Cab lights and side lights for all of the T-Series you have made.