Pool house// Tiny house

Im essentially putting a tiny house in my backyard. Due to zoning laws, we will call it a pool house. It will be 30'x10', and can be 18' tall, built on slab. Im thinking 2 lofts on opposite sides for beds. There's an existing concrete pad in place that I'll be adding on to, so all plumbing has to be done on the left side. I want the bathroom all the way to the left, which includes a good sized vanity, a 36"x36" shower (no tub), and a stacked washer and dryer. The kitchen and living room will be the remainder of the ground level. Planning for the water heater/misc. utilities is where I need the most help. Appreciate any interest and consideration!