How about full fenders and a cape?
Seriously, the best waterproof pants are the ones you don't wear.
Instead, think highly water resistant, stretchy tech fabrics, water resistant construction, active pants from The North Face, Columbia, Marmot, Arcteryx, Outdoor Research. stretchy, dry quick, work hella for biking. Stylish, urban commando look. Way more svelte than rain pants, hello!
OR,
try tailored pants in cotton with Nanosphere, stain resist or other DWR. Roll up to above the calf, and go for it! New fabric tech is doing amazing things with natural fibers.
I have some great, light gauge cotton pants from Filson with DWR that are nice enough to wear with a sport coat, but I can commute to and from work and around town with them. Even after riding in a rainstorm, they dry out within the hour or so after coming inside, its really wierd for cotton. I ride in these in Seattle all thru the winter.
Unless you need to commute in your tailored wool 120's, I'd ditch the waterproof pants idea and look at a better pair of pants.