Originally Posted by cranky old dude

Every bike I own has become into an impromptu "rain bike" at one time or another!

Moral of the story.....Pick up a bike you like a lot and set it up for foul (or fowl) weather. Good tires are probably a plus but I have found that I generally slow down quite a bit on wet pavement anyway. It's hard to determine the depth of road puddles (some of ours seem bottomless), and the pavement markings can be as slick as grease when they're wet. Our dry spells don't often last long enough to create much of a slipage hazard on the blacktop surface at first wetting as the surface is usually pretty clean. I'm running an old pair of GEAX Street Runners on my commuter that are almost bald and I haven't been noticing any traction problems. The recumbents are shod with Schwalbe Marathon Plus and when caught in the rain they handle quite well, though they're probably heavier than you want for a road bike.

Beyond fenders and good bright strobes front and rear I think all you'll need is a stepped-up maintainance program to keep things nice and lubricated and rust free.

I like your idea of using a road bike, as your riding position should cause most precipitation to strike your back. I've been caught in heavy downpours on my recumbents more times than I care to recall. What I remember most is how those wind driven giant rain drops sting the thighs and face.