I don't know if this is going to be helpful but here is my take on this.
Trying to decide on fixed groupings for items, most of which are probably not of critical concern to small vessel operators is, in my view, not an ideal approach to nautical (or any other) information dissemination.
It may be best to consider a general purpose schema that de-couples information from presentation. Define basic data types (take your pick, from those in S57 data definitions to any modern language), define structures etc.
With that you can have data producers specify items as needed, together with a few *simple* presentation and and ordering suggestions. The data schema would also deal with updates, synchronization, data verification and other such issues.
Presentation would be separate and flexible, such that whatever data or object type you provide, can be grouped with and presented with other objects on a client side.
Then map this to a commonly accepted data format (XML will work for data interchange, and vendors can re-map for performance), perhaps make it compatible with GPX to maintain at least a small level of continuity. The result will be easier to use and good for everyone.
Just my 5 cents worth.
Polar Navy - because life is too short to use ugly navigation software