Don't know how many circuits you're having installed. My 2 sheds share a 60 amp sub panel, divided into 3 20 amp circuits. Each circuit and outlet is color coded so I can split the load. I have all LED lighting so I can use the same circuit for light, heat or AC. I keep two circuits open, one for whatever tool I'm using, the other for the dust collector. Do wire and insulate, then install drywall, then paint. MUCH easier to keep clean. Out here there was no electrical permit required. The second shed is 10x12 and is a small office where I do most of my printing.
Insulate the ceiling. If it has 2x6 beams, put up R38. Find a way to seal the doors. Probably too late now, but I would have put in insulation under the floor if I had to do it again. I also lined the ceiling with that reflective, aluminized bubble wrap, which reflects heat out in summer, in in winter. It's only R4 but it makes a difference. Do the insulation and drywall BEFORE you put a single tool in there!!!!!
My shed is 12x24 and it looked huge at first, but I eventually outgrew it. Since yours was built in place, it's probably level, mine is not. So you could add a same size deck in front, then over time enclose and cover it. You're going to be taking tools outside to use, so putting a deck out there the same height as the existing floorwill make it easier to roll rather than carry your tools outside. Last item: The 1 inch ply floor in my shed is not all that solid, consider putting a piece of 3/4 ply underneath your table saw to prevent wobbling.
Really nice building and I understand what you mean about better to get a somewhat smaller shed rather than have none. I predict considerable enjoyment ahead. My wife likes me spending time in the shed, close by, but not under foot. Keep your cell phone handy for emergencies.
The more I do, the less I accomplish.