Random threadjack, but does the Navy have any O-4 or lower commands?
A couple good ship examples are the minesweepers (normally O-4) and the PCCs (O-3). Good examples of ashore commands are the NOSCs (reserve centers), which are billeted as O-3 through O-6, mostly depending on the size (sometimes with +/- 1 paygrade flexibility, sometimes not)... off the top of my head, I can't think of any others.
As far as aviation, I don't think we've and any O-4 or below command for decades now.