There's still the issue where wearing double gloves will prevent the wearing of gauntlets (2 gloves = total size 20, so gauntlets with permit 15 can't be equipped). While double gloving is a valid vanilla combo, sometimes it's not what the player intended e.g. I want my dwarf to wear leather gloves specifically, so I set it as part of the uniform. But at the same time I want to let them wear what they like (trinkets, etc) so I set it to wear over civ clothing. The dwarf then decides to keep the silk gloves they had on, puts the leather ones over it, thus preventing the use of gauntlets. Sometimes they'll skip the leather gloves and just put the gauntlets. I even had a combination where one hand was wearing 2 gloves and no gauntlet while the other only one glove (the original personal glove) and the gauntlet.

At the cost of sacrificing the vanilla combo, I'd suggest the to also make the following changes if anyone wants to do it manually or make their own mod:
Change glove permit to 5 (effectively preventing the application of double gloving)

This change will not force the dwarf to abandon their civilian gloves for the ones you specify, but it does make sure that they don't double glove and prevent the more important gauntlet from being worn. I'm hoping that when they finally get rid of their old civ gloves they'll go for the ones I specified and stick with it until it breaks/rots (but if you set them to not wear uniform while off duty they'll probably just pick up a different pair of personal gloves again).

This issue also comes up when assigning socks as part of the uniform, so the dwarf will try to put two pairs of socks which prevents the use of boots, or skip the specified sock and wear the boot. Reducing the sock's permit below its size also partially resolves this issue (again, removing the vanilla combo of double socking). However, my suggested fixes are not required for those who don't specify what non-armor clothing their military should wear, and especially not for those who prefer to use replace clothing command. If you prefer to avoid these headaches, just don't tell your military what non-armor clothing they should wear.