I'm thinking of this too but whatever mesh you put there as an alternative would still restrict airflow if you put it on a flat surface. If you look at the rubber(ish) border on the bottom, there are cutouts on the front and back which work as air "intakes" when the laptop is on a flat surface.
For now I've gone a different route, i took a 40x30cm board, put a layer of cork on top, and am using that on a laptop stand. Still the same airflow restriction but greatly reduces perceptible fan noise. And i can get it propped up. But definitely would like to improve this so that there is no restriction at all; i don't mind compromising portability because i only move it a couple times per year.