mporter- I'm not sure what your subject matter is but, based on your snow example, I'll assume it's landscape. The truth is, most of the time a roll will require either N, -, or + development, not all three, (which you can't do anyway). Unless the light is changing rapidly, your exposures will be fairly consistent, assuming your subject matter is consistent. Any slight variation can easily be addressed in printing.
Carrying 3 cameras will be a waste. You'd be better served by using 20 exposure rolls (or bulk loading even shorter rolls) than carrying the extra cameras.