I have heard some horror stories from some of the HVAC guys here in Northeast Pa about the concrete not being so friendly to the pex tubing.
It doent like the expansion / contraction thing as well as the chemicals from the concrete while curing.If it springs a leak for whatever reason ,you cant fix it.
Honestly If it were me, I would put in radiant baseboard around the perimiter of the shop, use an outdoor boiler and an oil fired one for backup with a heat exchanger. There are outdoor woodstoves that can be multifueled, but I have checked into that for my remod, and they arent as efficient as putting in a dedicated unit.
With radiant it feels warm all the time and it is very even heat. Fanforced only feels warm when it is running, it stirs up a buttload of dust and its impossible to put the "unit" outdoors to contain the burner away from the air in the shop(VOC , solvents thinners etc. explosion...you get it)
I like the outdoor woodburner my neighbor has, itkeeps his house at 80 degrees inside all winter long.
I have an oil fired burner and my house is small and tight, I have used 275 gallons of oil so far this winter.
If oil keeps going up, I will be getting an outdoor stove and putting in a heat exchange for the hydronic (radiant baseboard) system in my house. If the fire goes down at night the oil fired boiler will pickup the slack.