I mentioned the pants/shirt issue to the staff at my FLMSS* the other day and basically the only thing special about army shirts is the camo dye job. Otherwise, yeah, they’re pretty similar to any buttondown shirt. Maybe 2 storage for the pockets, but nothing major.
(IIRC dress shirts are encumbrance 1, though, so you’d probably want some Tailoring if you’re a melee type.)
*Friendly Local Military Surplus Store