For our product (payment terminals) the sound feedback is crucial to the experience especially during the different transaction flows. We would like to be able to easily create prototypes with sound feedback to experiment and improve the sound feedback on our devices. To have maximum flexibility this could be just another available action under Interactions. Since it is only sound feedback a file size limitation would be most likely not a problem for us.
I can see how this can also be very valuable when designing apps with e.g., notifications. I am pretty sure there is more need for this out in the design community.
Feel free to add your use cases and start discussing…