Now if only you can assign civilians armor, my humans would be invincible.
Humans?!

Anyway, What I find works really well is to assign all civilians to squads (except miners, hunters, and woodcutters. They're bugged

). I make a custom Civilian uniform using leather armor, leather legging, any low boots, a leather cloak, leather hood, leather cap, metal helm, wooden buckler, and any short sword (just some basic stuff that won't overburden and slow them down too much). Since "clothing" works properly, now, you can just set it to "wear over clothes," or add trousers, shirt, shoes and set it "replace clothes." I guess next version armor will count as clothes so this will be easier.
Anyway once you do that, just confirm in their schedule it's set as "wear uniform when inactive" (the default setting), and then leave them as inactive forever, don't build or assign them any barracks. They will now act exactly like normal civilians, except they will armor up and grab swords (you can make them do this faster by issuing a "move" command to the armor stockpile). You also have the option of stationing them somewhere quickly if you want, but I just stick to burrows for that. Make sure to set their priority below your military in the military menu, I think (m) > (e) > (P), then put them at the bottom of the list (so soliders get priority over civvies on picking good armor).
Also make sure to set them to not carry any food with (m) > uh, (u)? > 'carry no food.' I find it handy to keep re-rolling the squad name until it starts with a "C," for Civilian, to keep it organised (though I guess in the new version you can nickname squads manually. Yay

)
This has always worked perfectly for me. Back in 31.25 I always used "replace clothing" since they didn't get unhappy thought from being naked, and wouldn't automatically reclothe themselves.