Thinking the same thing myself as the cooler weather sets in. Rather than dropping 200+ on winter shoes I think I'm going the light weight hiking boot/platform pedal combo for the cold and snow. Been wanting to try platforms again anyway.
CX racing doesn't really matter though, does it? You can handle the cold for 45 min (if you even notice it while racing) and then you change quick after the race.
I recommend waterproof over shoes. Shimano have good ones.
I have Sidi winter shoes which are waterproof. It doesen't help because water goes inside from top of the shoe. The closure system is really poor. If you put it tight enough strap pop open when you twist your ankle.