This has now been done, in the diaspora* federation protocol library. This work has improved federation performance immensely, and has also added support for various features to be built. I’m not 100% sure whether federation support for editing has yet been implemented, so let’s ask @supertux88, who has been in charge of work on the federation protocol.
By the way, even if you’re an experienced RoR developer, I wouldn’t recommend starting with the editing, as that’s going to touch many different areas of the code. If you can find some other PRs that would first familiarise you with the different areas that editing would involve, it would help you a lot. I’m sure the core devs (I’m not one) will be able to suggest some tasks to work on first to get you acquainted with what will be needed.
It’s great that you’d like to tackle this much-needed feature!
Edit: oops! Sorry, I thought this was the discussion about editing posts. So some of what I wrote is irrelevant, but some still relevant. I’m not sure how much less complex groups would be to implement than editing, but the core devs will be able to help there.