Well,

since setting up any structured environment in FrameMaker includes dealing with the EDD, you could take advantage of conditional text in the EDD document to include/exclude certain parts of the structure.

Or vice versa: Have different EDDs that join common parts in form of text insets.

For a certain project/customer/product you usually have a defined, fixed EDD, but if you want to support multiple projects/customers/products with similar structures this might be an option.

- Michael