Has this ever been considered?
I believe we had an exporter for a subsystem once, but it was discontinued as nobody was really interested in it.
There is a class/plugin in bnd called: aQute.bnd.exporter.subsystem.SubsystemExporter. I, however, see that the package is not marked with ;bnd-plugins=true. This means bnd won’t discover it.
If this is useful we can add it.