Considering that unless you are making a living with it, the woodshop itself is a luxury item, I don't think a simple shower stall (and water heater, if slop sink OP mentioned was going to be cold water only), is much of a stretch. Few people bother to run water and drain to the shop, especially in a seperate building, but OP metioned a half-bath, so adding a shower to that becomes trivial. Unless a woodshop is a just a display room (like a yuppie restaurant-grade gourmet kitchen that seldom actually gets used), you do tend to get dirty working in there.
aem sends....