I believe that you can continue using the regular item binding setup in parallel to the MQTT Event Bus link.
For example:
With MQTT Event Bus configured to publish everything to:
statePublishTopic=openhab/out/${item}/state
commandPublishTopic=openhab/out/${item}/command
and a specific item (bound to mqtt) defined as:
Switch Robo500 "Robo 500" {mqtt=">[HomeR:HomeAuto/ESP/whatever:command:ON:default]", autoupdate="false"}
I would get the command message published to both topics:
openhab/out/Robo500/command (due to the MQTT Event Bus)
as well as
HomeAuto/ESP/whatever (due to the item config)
So, I am not constrained in any way.
Note: I haven’t tested this out but I believe that it will work as I described it…
It could get tricky with subscriptions (2 sources of state updates for the same item…)