That is likely to destroy the structural integrity of the stand. Trimming the mouse pad, while possibly a heresy, is likely to be easier and safer.
personally, I’ve been thinking of milling some stands and that are basically solid blocks of wood in the shape of the keyboard just cut at the angle I would like to hold the keyboard at. to do this properly, I world need to mill out little cut outs for the feet and the rails.
if I had just a little bit more free time, I could prototype them and put up the design somewhere.