What you have are the makings of the best bet for keeping warm. I don't think you're going to be able to keep dry, however. I use summer mtn bike shoes in the winter, generally start with a base layer sock (thin), covered by a medium or thick wool sock. Place toe warmers on the shoe insoles up near the toes, then another pair directly on top of your socks. cover your shoes with the neoprene booties and you should keep warm, even in you get wet. If you use the plastic bags, your feet are going to get wet with sweat - they don't breathe at all. One of the most important parts of keeping your feet warm is to warm up your core and legs, so make sure they are warm and you should be ok. Maybe carry some spare socks in a baggy if you need them.