The mat is extremely durable. The canvas back adds enough strength that the caulking on top won't tear when pulled. The caulking itself is durable on its own, it doesn't flake or peel from the canvas. Even with rough handling I can't see this mat tearing. I don't think using heavyweight canvas would add a lot of durability, I'd say it has enough with just the normal weight canvas.
I don't know how well adding sand/flock to the mat would work. I'd experiment with texturing the caulk with a variety of materials, and replicating the snow effect through paint first.