If you want to get off that cold concrete slab now's the time while the building is empty.

Dri-core panels are about $1.25/sf. Or just coat with epoxy floor paint.
https://dricore.com/products/dricore-subfloor/

Excellent suggestion on the dricore subfloor. I’m considering that exact product, but the budget is tight. I’ve considered grinding and sealing, epoxy and laminate tile squares. For now, I’m opting to stick with the concrete and use rubber anti fatigue mats at the work stations. I work in a warehouse distribution environment, so concrete floors and I are pretty familiar.

If you want to get off that cold concrete slab now's the time while the building is empty.

Dri-core panels are about $1.25/sf. Or just coat with epoxy floor paint.
https://dricore.com/products/dricore-subfloor/

Nice shop.  Looks like you're doing things right - with the possible exception of demolition (sorry about the stitches). 

+1 for getting off the cold, hard concrete. 

I put down 2" foam insulating board from a big box store, then put Advantech tongue and groove over it.  My feet, knees, and back thank me every day for doing so.  I'm in Wisconsin and my feet are never cold when I'm in the shop in winter.  No issues with rolling heavy stuff around either.

Best wishes on your new shop.