1. Head
UVex glasses, most of the time.
(a) rain: BMX helmet
(b) snow: Skullcap under bmx helmet.

2. Torso
(a) rain: rain jacket w/ the big pit zips.
(b) snow: softshell, sometimes with thin long sleeved jersey underneath.

3. Legs
(a) rain: tights+cutoff BDUs or rain pants if it's really pouring.
(b) snow: tights under cuffed pants.

4. Hands
(a) rain: wool liners under mtb gloves
(b) snow: above, or lobster mits.

5. Feet
(a) rain: wool socks + sidis.
(b) snow: lake mx300 winter boots.

- Knobby tires? How wide? If not, thicker slicks? How wide?
one bike with 1.9 studded nokians, one bike with 700X28 slicks. basically, snow/ice and rain bikes.

- Anything else you want to add:
fenders. on everything. zipties are your friend.
a change of clothes at work, or at least a pair of dry socks in the bag can make life a lot better.
If you can get access to a heat vent to pile the wet clothes on, it'll be nice and toasty by the time you need to head back out.