I’ll throw this suggestion out to you too – while a warm sleeping bag would be a good start, maybe a couple sheets of plywood to put over the truck bed with a tarp over that would provide you some extra protection from rain/snow and also trap in some body heat. You wouldn’t have to make them permanent and could just slide the wood into the bed when not sleeping under it. A cheap bivy as Ryan suggested would also be a good consideration and a quality sleeping pad to provide some warm rating and comfort from the truck bed.
While not as large as I would have liked (is a wood shop ever big enough?), it is about twice the size of my previous shop. It measures about 12 by 25. Fortunately I had managed to find quite a bit of shelving before the move, so I was able to install shelving along two walls. And the work benches were made from wood salvaged from packing crates from Europe and left over yellow pine car siding and flooring from remodeling the old house.
Cut off a 21-in.-long board for the shelves, rip it in the middle to make two shelves, and cut 45-degree bevels on the two long front edges with a router or table saw. Bevel the ends of the other board, cut dadoes, which are grooves cut into the wood with a router or a table saw with a dado blade, cross- wise (cut a dado on scrap and test-fit the shelves first!) and cut it into four narrower boards, two at 1-3/8 in. wide and two at 4 in.
Make sure to run ground wires wrapped around all lengths of flexible exhaust hose to prevent static build up, which can spark and potentially ignite. I chose the King 1.5 HP dust collector, with a 115 volt motor, so I did not need special wiring for it. A shop vac is a must, as well, used to vacuum out machinery, and to remove dust from furniture prior to finishing. Finally, an air filtration system was installed to clear the air of tiny airborne particles. The King KAC 650 unit I installed does a nice job, has a remote control, and a programmable delay – I usually have the air cleaner run for a timed two hours when I leave the shop.