Yes, but you could define the e and ratings tags as mandatory and the o tag as optional, and you'd have everything on earth and in the heavens covered.
Discussion
How does an hashtag have an e-tag? Or a movie have an e-tag?
Honestly I am done. Do your own thing. I don't think you grasp this fully yet. But if you think you've got it. Awesome!
Okay.
Oh, right, but something like o still shouldn't be a MUST, since it isn't used every time. It should be a SHOULD because you should use it when referencing something off-nostr.