New library type (design discussion)

(for a long time already) I want to implement the new library type (or any other) way to do the following:

GNU ar (with MRI file), as well as MS librarian (lib.exe), could combine several static libs into a single one. Nowadays few of my projects use custom targets but native CMake support for this can give more flexibility (like exporting, using the result for further target_link_libraries by name/alias, &etc.).

It should produce a static library that includes all other static libs (or OBJECT libs, or *.o files of the given sources) mentioned in the target_link_libraries (ignoring dynamic libs).

Here I want to hear opinions about how to implement it:

1. add a new library type to the existing STATIC, SHARED... e.g. smth like COMBINED_STATIC

    add_library(
        foo COMBINED_STATIC
        # Some sources may follow, but no sources also Ok
    )
   
    target_link_libraries(
        foo
        PUBLIC
            bar_static
            another_static
            ...
    )

2. implement it as a target property (e.g. setting COMBINED to TRUE)

    add_library(
        foo STATIC
        # Some sources may follow, but no sources also Ok
    )
   
    set_target_properties(
        foo
        PROPERTIES
            COMBINED TRUE
      )
   ...

3. maybe as a genex?

    add_library(
        foo STATIC
        # Some sources may follow, but no sources also Ok
    )
   
    target_link_libraries(
        foo
        PUBLIC
            $<COMBINE_WITH:bar_static;another_static>
            ...
    )

What do you think?