I was so glad reading a post from one of leJOS' developer where he mentioned that the new version will have support for raw PCM files from memory! This effectively solves all my problems with unsufficient audio support. Though, with some further experiments, I got a rather concept for polyphony using it's standard playTone() function. It may sound rather weird with many tones playing, so I'm glad that there will be support for it. However, I can still implement and perfection the design I had in my mind - it should work fine with the current quick'n dirty polyphonie mixer and the one for later firmware. So when the next update time has come, I can simply extend it to feature both ways of mixing multiple voices. I'm quite optimistic about this one. And it's also a good reference work using limited ressources but still offering a flexible feature palette.
Anyway, I'll have to freeze this project for a while as I'm now entering the hot phase of the current semester. I need to finish my PGN database interface (one function is still missing), write a little image processing plugin and prepare a talk about risk management in a project of my choice. And well, then there's this fucking Flash rabbit project for my sister.... So annoying.