Is there a way to extend default assets (images, videos, etc) with extra fields?

I’d like to be able to use rich text fields for image descriptions or add my own custom fields to assets; is this possible to do?

I could create a custom Image model or something, but my application has gotten so large that it’ll be a pain to go through and change all the references around.

Not at the moment - your workaround is the only solution for now.