Ideas
I guess I'm just concerned that an attempt to fix all mismatching could result in the fashion equivalent to Sims 3 pudding face. I know that's exactly what some of you want, but I would rather my townies be individuals.
I would be open to a color coordination modification where each townie has a randomized color and their assets are filtered on that color, sort of like the color dress code from Get Together, but for an individual. But trying to impose pre-approved styles would make the townies too uniform, imo.
The thing is boring townies can always be jazzed up. Have you seen some of the way Sims 4 CAS categorizes things in the same catergory/style preference. For those invested in deeper Townie specification mechanics, there can be deeper control. But it is a game at the end of the day, the more complex you make the rule set the more opportunities to end up right back where we are. So simplifying what Townies can choose gets you part of the way to stopping random peircings, bows, hats, etc etc.
Having a styled outfits rule for Townies honestly solves a ton. Humans just pick better outfits then a randomizer/computer and will always. If there's a little bit of boring in that, the human player can jazz it up as it interest them.