Some more things from my shop.
Floor anchors are 1 3/8 Williams Form Engineering ASTM A 722 bars. Bars are anchored with a 1" plate, 40" under finish grade. Bars are in a pvc tube. Tie downs internal to the thick portion of the floor should be good to 75 tons per anchor. Bars are finished below grade with a coupling nut. Remove cover and screw a spare bar into the nut. There will be a crack around the heavy floor section.
Run electric conduit under the slab. I have subpanels on two walls. No heavy power goes over an overhead door. I have both 240V and 480V panels.
For your climate, lots of insulation. I have 3 1/2" under the wall and roof panels. After the structure was completed, 8" was added in the walls. The girts are fully insulated, with a white plastic on the inside of the insulation. 8' high white building panels line the inside. The roof purlins are also full of insulation. There is white strapping screwed on the bottoms of the purlins. Then white plastic was laid over the strapping, then the bats were laid on that before the roof was installed.
If you put doors on the south wall, get extra light panels. My south door is a 9 panel, the bottom 2 panels and the top panel are solid, the 6 center panels have 11? windows.
If its a cheap building they will omit a girt at 4' off the slab. You need that girt for strength and convenience of hanging stuff.
Put windows at 16' in the south wall. Put the office on the south wall.
Make sure the windows in the office are at residential height. My office windows are side sliders setting on the 4' girt. I don't like them. They should be residential single or double hung windows at more like 38".
If you have a budget problem and have to build smaller than you need, build the width and the height. You can always add length. Tell the builder so the end for expansion will get a full rafter.