A civilian uniform would be a neat thing to have. If you're too picky about it, you run the risk of having dwarves ordered to wear something they dislike(wrong colour, maybe, even if not based on the material), and any dwarf might get mild unhappy thoughts because wearing armour makes them feel unsafe(heavier armour causing a stronger negative thought, as might some prefs)(edit: e.g. "S/He was irritated/agitated/upset/alarmed at needing to wear armour lately."), but it would be nice if you could at least get them to wear leather. In more dangerous areas, the extra protection of mail would be worth the unhappy thoughts because the dwarves would still be alive to have them. And if the dwarf has a preference for that sort of item, they get a happy thought instead of an unhappy one.
I was initially against the notion of civilian squads(edit: not least because squads are currently limited to ten, so the management of a large fortress's kit would become tedious), but you might e.g. be content with leather for the general populace, but want your woodcutters, wood haulers, and herbalists wearing something sturdier, and I'm not sure how to reconcile that. Burrows wouldn't really work as a given citizen might be assigned to several, and they might have conflicts that are not simply resolved by the computer. Perhaps any given citizen could be assigned to a particular uniform category, and would seek out gear to suit? That would allow you to protect civilians according to their needs, without needing to group them into formal squads. There could even be an option in the uniforms interface to designate the default civilian outfit(which would be non-armour clothing by default), as well as each person having their own setting. Leave it at "follow default", and they will change as you change that master setting; assign them something more specific(even if it IS the current default), and they'll stick with it. (Edit: By that I mean that they'll maintain that uniform. Once you tell them to wear "Surface" or "Cavern" uniform, they will do so - but if you change what that uniform entails, they will alter their inventory to suit.)
Addendum: And if you suspect that a given dwarf is going to make a noble upset, you could issue them armour and hope they get it before the guards get to them...
You could even use this in a nonmilitary context if you could specify when dwarves will replace clothing. This could have issues with the economy, though, unless you have control over what they are issued from stores and what they personally own. Giving every dwarf a dyed and decorated +pig tail cloak+ might be a good idea in cold environments - the dye and decoration aren't essential, but the cloak is helpful and the ornamentation could make them happier to have been given it.