Found out about the Tinymovr motor controller. Basically what I'm trying to do! Very cool, and my version 2 will use it as reference. I hope to make mine even smaller (27x27mm vs 40x36mm) and cheaper ($40 vs €89). I only need up to 13V (3S lipo), while theirs goes up to 38V. Huge respect to their firmware too, lots of features there.