Agreed, hard wire it into the panel inside your shop, its way too soggy in WA to have the electrics in an unheated building outside.
If the little building is going to have a steel roof, make sure its insulated otherwise it will rain inside all over you new compressor.
I would nix the lattice too, 12" of that is leaving a big hole for the november rains to just pour through!
Something like a bathroom exhaust fan would be plenty of air moving around a little building with a vent on the opposite side.
Nice to have it out in a little room though, get rid of all the noise!
