Hi Scott,
as you may have noticed if you browsed the DVD audio Tools forum, there's a project to add multichannel support to dvda-author. An experimental version S has been devised for tests (not distributed openly yet).
Also, I've added to 08.07 and later versions an option for hybrid-DVD building, which does about the same job as DiscWelder Chrome (you can get to DVD-Video tracks from DVD-Audio tracks and vice-versa with your remote control by just pressing a group number).
I think it would be useful to integrate these features in a GUI, so I've been thinking of writing a Qt interface. However, as there is already your java GUI around, which is portable and pretty functional, another option could be to develop it by adding the new features. I could possibly do part of the job if you're too busy for it just now.
Just tell me what you think -- Best, Fab