Yes, theorectically this sounds like it will work. The only problem I'm seeing is what are you using as an input to the RTA? If you're using a microphone with a pre-amp, then you have to remember that both the microphone and pre-amp will affect the frequency response feeding the RTA.

I am an engineer for Harman International (ie JBL, Mark Levinson, Infinity, Harman/Kardon..etc.) and also a mastering engineer. This is a similar setup that we use to tune premium audio systems that we put in vehicles for Lexus, Toyota, BMW, Mercedes, Porche, Audi and Chrysler...etc. Our audio systems are tuned to each vehicle, and we use pink noise as a first stage of tuning to pin point troublesome frequency areas caused by the vehicles interior. We use an 8 microphone array, which get's placed in the driver's seat, and each microphone is turned on and off very quickly to not get any phase problems. This 8 microphone array is specifically designed for this type of measurement, to also give a flat response, therefore it is not altering the frequency content it is monitoring.

Your theory will work, but you may not like what you hear. Most audio systems are not tuned with a "Flat Response".

The best thing you can do after making your system flat, is to monitor many music CD tracks that you are familiar with through your system, and then make additional adjustments in the eq's, until they sound natural to you. Once you do this, then listen...listen...and listen..to the audio system using music that you are familiar with and get familiar to individual instruments and voices, to see how they transpire on your system. You're basically getting familiar with how your system sounds. Then do your mastering. Once you feel your mastering is complete, then go back and compare it to these music tracks again, and see how different the tonal quality and volume level is. If they're very similar, then you probably have done a good job mastering it. If not....go back and learn some more tricks and keep practicing.

Rednroll