@mikedev I've just re-read the whole conversation on GitHub and while I still don't understand half of it, one thing JSON-LD experts seem to agree on is that we need to copy @context from the document to the proof object during signing.
This means there will be a way to distinguish between 'old' and 'new' eddsa-jcs-2022, and that makes option (2) even more attractive. So I'll be using eddsa-jcs-2022 to sign activities.