I was thinking too that the natural progression would be to look at the tempo after the pitch. As a self-taught hobbyist musician myself, I could appreciate such a "gadget".
On another thought, is there anyone out there bothered by classical recordings that don't convey the sound delay from the back of the orchestra? Timpani and such. I'm still too new to this adventure to know if any of my music is actually recorded that way or not. I have just come to notice this as I took the steps from Jot -> Gumby -> Yggy and started to notice that there might be something strange with the perfect timing of the instruments in the back vs violin/woodwind in front. It seems this may not be as simple as delaying the bass response but what do I know