I'm pretty sure Ohio get's alot more rain/snow. I've no clue where you're located.

Far as compacting the rock, very minor detail a roller will smash the rock down pretty good and gravel on top rolled or shook down would solve that. Or a Cat, either way 1 day should solve the settling.

Badger is right about air flow. And considering the Ohio weather a couple of fans could move alot of air either pushing or blowing thru the barn on the back end.

Amount of rain/snow/wind is a factor in getting the air thru and keeping the elements out.

'Here' a "a few inches of rock, or limestone to the grade needed, plastic, and concrete poured on that. That applies to shops, machine sheds, grain bins, etc."  would not meet any building code. And would guarentee all the bottoms would be damaged.

As I said,, just trying to save years of grief after it's done..

to each his own...