Friendship and other non-follow relationships

For being a social protocol, I was somewhat surprised to see that there are no FEPs around something as basic as friend relationships or other social relationships (at least, I didn't find any).

Currently, the only relationship that ActivityPub really defines is the Follow relationship, i.e. the asymmetrical relationship where Alice follows Bob, because Alice would like to see all the activities that Bob produce.

The ActivityStreams vocabulary does talk about relationships in a more general manner, but it is quite vague and this (afaik) doesn't seem to have translated to a wide usage of this approach. It even talks about how you could model requests of those relationships, i.e. friend requests, via the Offer activity with a Relationship object.

Are there implementations out there that use the ActivityStreams' (somewhat loose) definition of relationships and relationship requests? I saw Friendica has this page on "Making Friends" and just from the name of Friendica, you'd think they'd have some notion of friends and friend requests. But from that page, I'm not sure how Friendica represents friends or federates those requests. And are there any other implementations out there that have relationships other than followers and requests for those relationships?

Would it make sense to write an FEP describing the approach laid out in the ActivityStreams vocabulary in more detail? I feel that such an FEP should at minimum cover the usual case of friends and friend requests, but ideally should be generic over any kind of relationship you could imagine (or perhaps at least any relationship defined at https://vocab.org/relationship/).

Or would it be more sensible to implement an approach, learn from that and write an FEP later?