Interesting thoughts. One thing I would suggest is avoid having ROS1 and ROS2 both utilized in these systems as shown in the diagram directly above. ROS1 will be end of life in about 1.5 years and while it will probably still get some usage that will be due mostly to legacy code bases. ROS2 could certainly fill any role ROS1 could. If you want to interface with legacy systems better to just add a bridge node instead of a whole ROS1 layer in your theoretical architecture.
In terms of a ROS specific architecture, this makes me wonder if there is value in a common message specification for “prompts” beyond just raw data (text etc). Is there some metadata common to prompts which is useful to capture and might help LLM/LWM interoperability?