if your thinking about heating your shop, also consider throwing a wall up down the middle to minimize what your heating
my barn is 50x50 with a 30x50 loft, i heat a 20x30 shop year round, i can also heat a 15x30 bay
the rest is unheated and also unheatable
as for plumbing? a sink is nice, but i don't consider a full bathroom necessary nor do i have one in my barn
i live country-ish, the world is my urinal and i can go into the house for anything else
floor drains usually end up plugged like your garage drain and they catch creeper wheels, nuts and that irreplaceable c-clip that popped off