I've seen a hider for multiples of hats, so I believe it is possible, but I was wondering if there is a mod for hiding other kinds of clothing. In my medieval neighborhoods, I'd like a way for any new sims born/moved in to the town only wear medieval clothing, so even something that could just wipe out all default clothing would be fine. Does one like this exist/could someone make something like it?

This is very close to a request; normally these are not allowed, but because this is something more than a few people may want an answer to, I will give a brief explanation on how something like this could be accomplished.

First, you will need to make some default replacement clothing. The objective here is to disable the clothing from being available for random. So you will need CTU; in CTU, make default replacement clothing, but in the part category tab, un-click the valid for random option, click commit, then save the package. You will need to do this for each article of clothing you want disabled. If you need help with CTU or a tutorial on how to make something a default-replacement, there are tutorials and threads to assist you, you just need to search for them.

Next, you will need jonha's Any Game Starter. I've never used the app myself, but from what I know about it, you are able to set up profiles that will only load certain sets of cc. So make a profile that contains all of your medieval cc and the default replacements that you just made. This should effectively remove game clothes from being rolled randomly and will make only the your medieval cc clothes available to spawned sims.

It's nice that you gave such a detailed answer Rez Delnava but how this is a request is beyond me considering the asker says "I was wondering if there is a mod for hiding other kinds of clothing." and it isn't til the end that they ask if it's possible to do so.
I'd never seen the hider before sugarcoatedfangs. Thanks for letting us know about it!