You can get the lockable shell up and grading set, wrap with insulation and Tyvek complete from sill plate to roof peak then wait until late spring to finish. Tyvek with taped seams (wow that stuff is sticky) will handle 50+mph wind, rain or snow what have you. Your contractor can show and enforce Tyveks warranty.

Last I heard unemployment for construction workers was 14% so don't think you'd have trouble finding good ones in the winter.

Yes steel roofs & siding can cause wireless difficulty but it's easily overcome whan adding an antenna and system inside; plus you're better protected from the effects of solar events too (EMF pulse).