Well, for the record, I am a professional user in every sense of the word you could imagine. I'm being paid to design and develop audio systems running on Linux, and that is my main source of income.

If it works, and if it doesn't make a mess of the calibrated gains for each channel, and if you can convince the users of this system that they need it, you will be paid very well and then you can consider yourself a professional.

A simple environment variable tested by all apps will do (e.g. something similar to 'EDITOR' which is used by most apps that need to start a text editor). Any app that directly connects to the sound card, without even offering the option not to do so, is like a musician walking into a studio and plugging his synth directly in the the control room's power amps. Even if he promises not to do that again next time, there's a good chance he won't be welcome anymore.