A point which cannot go without saying is that any software-based solution for use in HCI must have latency characteristics that are below human perception. Acceptable latency is a function of context. If you start some music in response to a user input you might be able to accept a delay as large as 600 milliseconds. This is a serious issue for Microsoft operating systems. Finally, audio services must be at the system level like mouse support or keyboard input.
Applications can get exclusive use of the one audio device.
Instead, the system should virtualize the wave device. The Microunds experiment referred to above is the first in a series of explorations that are ongoing in my group. We hope to cooperate with your efforts in exploring this problem space. There is another whole set of issues that is related to the attention getting properties of HCI audio and volume that need to be solved if we are to get this right.