I think I am going to start with the patch and selectionchange and see how far I can get with kakscript, it isn’t much data most of the time, just shuffling text over pipes.
I agree that an alternative to might be the way forward as it would make somethings alot easier and allow it to be written in something else then kakscript.
I don’t think there is any way to have an custom ui and an standard one at the same time. For blind users that wouldn’t matter but if you want see the buffer being read that could be an problem. You could still have to kakoune clients open at the same time, one TUI and one SUI but the to wouldn’t be synced (but the could be contacted to the same kak server.
Haven’t dug to deeply in to the hole kakoune custom UI thing (kak -ui json) so I don’t really know how easy it would be to make an SUI using it. One thing that worries me is the communication between the UI and the kakoune plugin (seems to be needed for commands and keybindings).