JSON-RPC interaction with running client(s)

Feature

It would be nice to be able to interact with Kakoune clients via the JSON-RPC, instead of just using it to build a GUI on top. For example, being able to send keystrokes by following the steps on the wiki. To disambiguate between clients, maybe the JSON-RPC id field could be (ab)used to contain the name of the target client for running the commands?

Usecase

I'm trying to find ways to work around https://github.com/mawww/kakoune/issues/3988 (at least while it's still in / awaiting discussion), and came across the JSON-RPC wiki entry. If it could actually influence a running client, it would become an easy way to interact with the clipboard (once a register method is implemented, which I have a local draft of).