It sounds that you have exactly the problem I faced some years ago.
Please have a look at MPDCenter, that has currently no help file (sorry), but should support you in your plans.
If you have any question about using it please ask, ask, ask
I designed MPDCenter to merge several mpd files into one new mpd file. MPDCenter can merge a mpd file to a ldr file.
I think it should be worth a try, if you are working on a windows machine.
Please have a look at MPDCenter, that has currently no help file (sorry), but should support you in your plans.
If you have any question about using it please ask, ask, ask
I designed MPDCenter to merge several mpd files into one new mpd file. MPDCenter can merge a mpd file to a ldr file.
I think it should be worth a try, if you are working on a windows machine.