Borrowing from the LISP concept of program as data, it could be interesting to try store functions as custom JSON and be able to compose them into a program by simply fetching them from the blockchain and running them.
A potential use case for this would be custom WebGL shader code to be applied to NFTs
It is an interesting idea. Function is a text, so you would be able to store it and retrieve the text when needed. But you would need that function processed somewhere else. I have thought about it in the past, not sure if this can add any efficiency though.