I appreciate that. There should be no need for OH1 bindings anymore at some point hopefully.
I mean, you can go with MQTT2 as well (see: https://github.com/openhab/openhab2-addons/tree/master/addons/binding/org.openhab.binding.mqtt.generic#synchronise-two-instances), it is just a bit more work and will not work reliable in OH 2.4 (you must be on OH 2.5M1 at least).
I’m a bit busy with the new Paper UI design study (https://davidgraeff.github.io/paperui-ng/) and all related missing core features. On my personal agenda it has a very low priority so ETA is about half a year to a year. Maybe someone else jumps in in the mean time.