That trip idea seems very awesome. Planning the gear Id focus on things that have incredibly low volume to performance rather than weight. Down bags, (either one puffy winter one or 2 summer weight bags that add up in loft) wind shells, bivies and/or tarps come to mind. For a sleeping pad, you may consider a winter weight inflatable pad that can perhaps strap onto one of the panniers and save a little volume inside without bulk. If your a member here, look at the icebox gear list, if your not, the same thing is on Andrew Skurka's website, http://www.andrewskurka.com/ICE07/gear_list.php. He uses alot of interesting ideas, such as vapor barriers for protecting his insulation from moisture, he also uses an alphamid and breathable bivy combination.
If your willing, the Oware Alphamid tarp is probably the lowest volume shelter to take the wind, and it can fit 2 people, for 25 ounces and its reasonable at $135. It requires a long pole, but they sell a collapsable one that won't get in the way. If you get a bivy like the equinox ultralight bivy, Black Diamond Epic bivy, Oware Epic bivy, or montbell bivy, you will be able to have a waterproof floor for your bag and then also have lots of free room to put dirty stuff in, or you could make a ground sheet out of Tyvek or Sil nylon, Oware may also make one for their tarp.
You want either a liquid fuel stove, or a canister stove with a fuel line, so that you can turn the butane canister upside down and run burn the liquid. This is much better for cold weather performance. For food, you should consider resupplies from mailing food to post offices ahead of time so you don't carry as much, and use lots of energy bars and boil in the bag type foods to help make it easier on you by not having to carry a frying pan or so on. Freezerbagcooking.com and packlitefoods.com are some good places to get ideas from.
Down sleeping bags are really expensive for winter weight, but you would be best off buying the best 700-800 fill down model you can find, as they are the lightest and most compressible. Montbell makes some excellent cheap bags, Western Mountaineering is also a good place. As i said earlier you could get a 20 or 30* bag, and then put it in a quilt like the ones from jacksrbetter.com, and get a whole lot of down for less. Synthetics are temptingly cheap, but consider how much space they will take up before you get one. If you can, get a dry bag, nothing to intense, to protect your bag from any moisture while its packed away.
Try and minimalize the small thing you carry, like first aid kits, bike repair, headlamps or lighting, see if you like Dr Bronners for toothpaste, soap, and everything else they are for, but make sure you don't let it freeze. Carry as little electronics and books etc as you want, would a map and compass be better than a GPS, and how small of a camera do you have or can bring?
For clothing, you have to have to anticipate your high exertion wind sweeping biking, and your stationary camping. psychovertical.com has some cool ideas for clothing in high wind alpine conditions. You may want to look into something like the Golite momentum jacket, which is virtually wind proof, or something from Montane, Marmot, or Buffalo teclite, that blocks wind and provides insulation.
Thats basicly evreything i can think of right now, there are people who know alot more about biking around here, but I hope I helped you out at least a little
