I suppose more people might already have started working on this or have ideas on how to do it? If so, please tell me about it!
If time and energy etc permits I would love to look into a way of doing this asap.
Use cases: if you want to contact someone specific atm, the best way basically is to comment on a post of them, or probably create a post mentioning them. This comes across a bit annoying and it's everything but private. Also communities start making inroads on dividing concerns of things you post but it's still not as on target as in some central systems.