[DaveBlake]

Since I never listen to both outputs at the same time, it dawned on me that rather than dual audio all I really need is an easy way to change the standard audio output settings from one set of parameters to another. By "easy" I mean without the TV being turned on, without menus to navigate, and to able to do it remotely as well as from the keyboard attached to my RPi.

Then I read this how-to thread and had a light-bulb moment.
I can use JSON commands to swap the audio device parameters. HTTP the right line of code from a web browser and it switches. All I have to do now is somehow put a nicer UI on this. Something to capture the settings, and something to run a Python script in response to a key press or icon click on my Android tablet etc. Maybe some kind of addon? Bit vague on those aspects for now.

Now this approach is not going to help those DA users that want to have multiple audio outputs simultaneously, sorry about that. But Gurabli it will replace the way that you are using DA, so that's 2 of us that could move back to official Kodi.

Edit: Such an addon already exits! See Audio Profiles. Hope the link helps people in the future - don't use dual audio if you don't need to.