A toyhauler would be a great choice.
If you prefer to go the class B route, an enclosed cargo trailer would probably make a suitable workshop area more easily than a travel trailer. You don't really need the double bathroom, bedroom, and kitchen facilities. You would probably need (or at least want) to add some lighting and ventilation and wiring to a cargo trailer, and maybe some heat and/or AC depending where you're intending to be, but that doesn't necessarily need to be too complicated. A small household window A/C unit set in the wall (with suitable supporting framework) would work just as effectively as a roof mounted RV AC and be a whole lot less expensive.
