If you are really interested in making a thinner stiffer pick I would experiment with learning how to harden and temper the high carb steel spring stock.
Here's the somewhat non-intuitive bit: heat treatment actually does very little to the stiffness of steel (stiffness being defined by the Young's modulus, which relates strain to applied stress). To do that, you either need high alloying, or an entirely different material. Having recently bought some nice 301 spring steel picks, I can't see having to apply any more force than I can with them. However, I'm still going to take a crack at different pick materials in the summer. Carbide may well have issues with brittle fracture. I'm also interested in trying a ~90% tungsten heavy alloy, which should have an elastic modulus roughly twice that of steel. Considering that these alloys come standard with sufficiently high tensile strengths and are considerably more workable than carbide (while having about 70% the Young's modulus), they may be a better option.