I probably wouldn't be able to fit the frames of animation I want into a pico cartridge, so I decided to try a different approach. After a couple of days of thinking and one evening of coding, I now have a kinda-working node-based vector skeleton animation system:

It's about as sturdy and flexible as my actual skeleton (not very), but it should suffice for this project. Next steps: Finalize the model and add animations.
Edit: Apparently, Itch doesn't want to show my animated gif. But trust me, it's pretty neat.
Edit 2: Hosted the gif here.