Hey, OP. Haven't checked this thread in a while. If you haven't built yours yet, I'll be more than happy to share my contractor's info with you. Also, since we're neighbors, I will be happy to let you see my shop and share lessons learned during construction. I had mine built as a shell with doors and then did the floor the following year and the power the summer after. Spread the cost out a bit and allowed me to plan the layout as I went.
My floor is 4" with no rebar or wire. Earth was compacted prior to the build. Gravel floor put in after build and equipment, camper, truck parked a drove on it for about a year. Area was leveled and floor was poured and finished. Control joints were cut the next day. No stray cracks, no movement in the floor. If I had done this in Ohio where I grew up, my floor would probably be a mess. Our sandy clay soil and our lack of freezing weather are very forgiving to things like driveways and foundations.