Is any one of you running an Ultimate Pedal?
I installed one with the upper left extension (check out their site to know what that means). The end result is that in heavy braking on track I heel & toe with the ball of the foot and heel on the gas (foot turned at an angle towards the brake pedal), but I can still heel & toe when braking gentler by just rolling the right side of my foot onto the gas (breathing on the gas with the right outer edge of the foot). That is made possible because my gas pedal is both a bit higher (thickness of the aluminum pedal) and a bit wider (pedal extension). It's close to the point where I can try it on almost every downshift (except traffic crawling), for practice.
They're not expensive or hard to install, I think if you have a bit of trouble doing the heel&toe you should give it a go.
2009 E90 M3 ED
2014 X1 28i