Today all of those are dead now in favor of ActivityPub. AP loses a lot of the simplicity that could make RSS ubiquitous (you need a home server and na application server to handle api calls) but the expected interactions are all there, and it's built to be extensible.
In fact, I think reusing the "everything is a file" is definitely cool and makes things easier to try, but you would definitely benefit from using the whole JSON-LD taxonomy. Things are already defined and have been used for some time in production, so you can expect some work has been thrown at it. It'd also make collaboration easier.