Hence why most smart labourers and contractors use a cargo van. No pesky seats blocking access and taking up space. Lots of customizeable room in the back for storage and shelves. Tall vans you can even walk inside and use a workbench. Many vans also have a decent towing capacity. Bed height is typically lower on a van, making heavier items easier to load. A lot of the same items people typically fit in truck beds can fit in the back of the van with the added benefits of being out of sight of thieves, being protected from weather and dirt, possibly even being heated or cooled if required.
That could be solved with an adequate partitiion installed (partition seperates the cab from the cargo). Many places require a work van to have a partition to prevent tools from entering the cab area when driving. The partition could be made to be comepletely air tight blocking fumes from the back. A sparkless ventilation system could even be installed if required.
This all may sound like an expensive upfront cost but it sounds worth it to keep expensive welders and such dry from rain and clean from road dirt.