Sorry, should have said the difference between ceramic and steel BB isn’t big, but BB vs journal, yeah, very worthwhile difference!
Back in my GT30 & GT35R days, you can hear the turbine slowing down for ages after switching the engine off.
I guess it depends if you want a bolt on replacement, or want to get involved with the faff of fitting a completely different turbo! It would be great if a turbo company upgraded the K04 with a BB CHRA. I’m thinking it would have been done by now if it was possible.
Have you dropped the downpipe to check for play in the turbo shaft? Should give you an idea of how much life it has left!