i might be convinced to write one, if i thought it was a good idea. i just am not entirely sure it is a good idea, because it involves entrenching mastodon’s power over the ecosystem even more.
or, well, you could argue that i already wrote such a thing at ActivityPub - Mastodon documentation i suppose?
yeah, mostly. although the types don’t need to specifically be Service and Collection. they can just be Collection, or there might be some extension type in there. in activitypub, any type can be an actor. it doesn’t have to be a Person / Group / Organization / Application / Service. (although again, most current implementations expect actors to be exactly one of these types…)
there’s more discussion of this at Unresolved issues surrounding Follow activities (from 2019!)