I had an idea for a project a while ago, and now that I'm actually more serious and looking into it I'm finding some issues. I guess I'll start at the beginning...
Plan was, to have a lighter duty but spacious truck to use and take kids, maybe a friend or 2 even sometime. Something not too elaborate, but slightly better than just a rig sleeper as in an extra bed and a shower. And lower cost.
I looked into using a crew cab 1 ton pickup and towing a bumper hitch trailer and have a truck box camper in the bed, but weight limits were an issue especially with any water tanks etc. So scratch the pickup idea.
Theres 3 and 5 ton straight trucks, but they almost all have tiny cabs with 2 seats. The crew cab models seem to fetch a premium maybe by people using for towing horse trailers and campers.
Better weight capacities and nicer engines than pickups. My favorite is the dt466 and 466e, reliable and easy to work on and do inframes on. Cheap.
And then we come to semi tractors. With the attached sleeper its sure comfy. I had this worked all out in my head and on paper. Find an old miled out tractor, repower it with a dt466 engine, build a box that sits behind the sleeper with an extra bed, sink, shower, etc. Install a pintle hitch and buy a pintle hitch trailer. Remove the front drive axle as it isn't needed for the desired weights and is just dead weight and tire wear.
At the rear of the truck frame I would make a hoist pole setup so I can detach the trailer and then lift up things with the truck and lower onto the trailer. It would be perfect.
However, where I live, semi tractors have a 8200kg rear axle weight limit (which would be fine) but a 6000kg front axle limit which talking to a few friends, their trucks are pretty close to limit on the front. So, it wouldn't be possible for me to add weight to the semi tractor between the front and rear axle as the front would end up overweight.
I do notice that straight trucks have a higher weight limit for the front axle, if the 5th wheel hitch is removed and using pintle hitch, can it be registered as a straight truck perhaps?
The last option would be finding a 5 ton frame and mounting a semi cab and sleeper to it along with hood etc.