Would a 50/50 mix of your audio with the sound of rain ruin the effectiveness of your tracks? If so then how about your track's specific rhythms and frequency changes but make them from sounds found similar to those in nature. I feel we have a deep relationship to the soundscapes in nature and to somehow combine it with your techniques would be amazing.
Well, I do like a good rain storm! There are already tons of binaural tracks on YouTube with music and sound effects layered on top though...
Brett Cameratraveler