The big issue is your neighbors, have you spoken to them? People get really upset, esp if you have an HOA. Seems that you simply say you're building for your hobby (soap making/tie dye), make sure it looks really nice. If it's not ghetto then you'll be ok, and it doesn't sound like it will be.
Electricity can be retro fitted later. Your sink issue, just make sure you have a wet wall between where you want your 3 basin and where the bathroom is, this way you can open the wall and will have direct access to H/C and drain. Really not much of a problem. Run a 20A 11V out for all your lights/outlets so it'll pass inspection, then after inspection, run your 240V and any extra 110V you need to a wall mounted sub panel, then run all your electrical through conduit outside the wall. Unfortunately, this isn't the pretty/fully finished version (rattle can paint the conduit so it looks interesting), however, when you go to sell the home, you can kill the extra circuits, remove everything proud of the walls and be to code. Then patch the walls, and the same goes for the 3 basin sink.
The floor drain is a problem and may be something you have to give up. Which totally sucks, but if that's the cost of getting it done, that's the way to do it.
Depending on your neighbors, the AC units for both the building and the cold room may be a problem. If they see/hear it that may cause you a headache, a mini-split will keep the profile lower but is more expensive. Same with the exhaust fan, you can add later.
I'd say the biggest thing is to know the inspection schedule. And lastly, your property taxing agency will want a piece of this too. So find out when they will come out to value it or what that process is before you start adding improvements inside and out.