My ex suggests a long apron - about knee length - split at crotch level so that it forms chaps. Farriers use something similar. Protects the legs and should be cooler than a full apron.
that reminds me of a question-- is keeping cool an issue? how much? i've noticed the commercially available bike shop aprons are thinner than our current stock. Cooks aprons need to be thicker/lined in case of spills, spattering grease, boiling liquids, etc, but that's not so much of an issue in the bicycle workshop, so perhaps a lighter fabric for cooler working conditions will prevail. what's your experience?