Another yes vote on a restroom in the shop. A lot of guys around here install a toilet flange with a short side exit pipe on it near a corner of the concrete floor pour, 1/8" below the finished level. This is installed right before the pour, then poured over and finished. Whenever a toilet is to be installed, a few taps with a hammer opens up a whole new world that inspectors and such know nothing about. A flange extension takes care of elevation issues, and a 55 gallon plastic barrel is then used to act as a septic tank, with about 20 feet of leach line. I built one in 1984 and it is still in use. My friend bought the property, and he thanks me for providing the restroom almost every time I am over there. My present property will have exactly the correct fall to drain into my existing tank about 80 feet away.