I don't know how many "feet belt" commuters there are, but I still use platform pedals & toe straps so I can employ a variety of different shoes.
Rainy commutes are always a challenge... I try to keep a worn-out pair of sneakers around for this duty, but they inevitably end up getting moldy, and fall apart soon thereafter.
I thought I'd pass you all this "find," of some cheap rain shoes:
I was perusing the cheap nylon sport shoes section at Payless the other day, and found a pair of Cross Trekkers Land/Water "all terrain" shoes for $14.99. These are much better put together than the slip on Surf Mocs that one uses when riding jet skis. They are neoprene and nylon, with thick molded synthetic rubber soles, and they lace, but instead of tying, they use a bolo-tie type of fastener.
The soles are stiff enough to allow bike shoe grade pedaling.
I tried them today on an appropriately rainy pre-dawn splash to work. 19.3 miles, through wet streets and a light but persistent drizzle, and my feet stayed dry! This beats having moldy ten year old sneakers hanging in my office all day...