What we really need is the sort of driver abstraction for the capabilities
   that the GUS provides.  With the GUS you can download samples to it and
   just tell the card "play sample that starts here and ends here, and play it
   over and over", and that sort of thing.

The SB16, at least, gives you a similar interface.  In fact, the only
interface I know for playing 16-bit samples (lacking documentation) 
actually requires this.

In reality, the audio system is already structured so that you more
or less have a `trigger' point where it starts playing or recording,
and it loops until you hit a `stop' point.  This, plus fixing a whole
lot of stupidity in the audio layer, is exactly what you're looking    
for.