About footwear for wet conditions:
For warm conditions, don't even bother to try to keep your feet dry. Anything that keeps moisture out will trap perspiration in. Get liner socks and otherwise prepare and train yourself so that you can walk in wet footwear without getting blisters. In very warm conditions (desert in summer), external moisture can actually be quite refreshing (putting hot feet into a cold stream).
For cold conditions, the best solution is probably the breathable neoprene socks made by Seirus and sold by Campmor, but unfortunately not in stock at Campmor right now. The neoprene has little holes cut in it to let water and perspiration vapor out. The effect is like a wet suit. Cold water leaks in through the holes, but then the water quickly warms up and stays warm because of the tremendous insulating capacity of the neoprene. Unlike some socks, neoprene doesn't wrinkle or fold when wet, so blisters due to wetness probably won't be that much of a problem (at least eventually--there may be an adjustment period).
W/B socks are nice while they last, and the Sealskinz versions actually last quite a while in my experience, but once they get a hole in them, they are a disaster. Bring along a spare pair for this contingency.
W/B membranes incorporated into the boot itself always break, and usually very quickly. At least with the Sealskinz, you are only out $20 when the sock springs a leak, and the Sealskinz only weigh about 4 oz, so you can afford to bring spares. But what lightweight hiker wants to bring along spare boots or can afford to throw away a pair of boots every week? Yes, a week is about how long the W/B membrane lasts on boots, when used under severe conditions.
If your primary concern is the weight of boots when wet, rather than wet feet themselves, I would suggest getting a fabric boot that doesn't absorb very much moisture. Or you could treat leather boots with various oils. It's been ages since I used leather boots and maybe they have some better oils nowadays.
Military mickey mouse vapor barrier boots will keep you dry and warm in very cold conditions, assuming you bring several pairs of wool socks and change the socks as they get sweat-soaked, but they are TOO warm for 3-season use.
Most lightweight hikers just use thin nylon socks with running shoes, which works pretty well. Sealskinz or breathable neoprene socks, instead of liner socks, would be a better solution for postholing and walking in slush.
I use Teva cross-tera sandals myself, with neoprene socks as required.
Regarding Mike Martins ideas, what he is suggesting is essentially vapor barrier technology built into the bag/garment. Stephenson has been offering that on their bags since the 1960's. The problem with vapor barrier on the bag alone is that then you then can't wear your insulated clothing inside the bag, unless the clothing is also protected by vapor barrier, which is something I have long been suggesting. Use a silnylon inner shell and a goretex outer shell. The silnylon keeps most perspiration out of the down or other insulation (and also keeps the insulation clean), while the goretex allows any perspiration that does sneak in through stiching to escape, and also protects the garment from external moisture (again, some external moisture could seep in through seams). The only two vapor barrier garments I know of that incorporate this design are the military Mickey Mouse boots, invented back in the 1950's, which are a true miracle product, and Bozeman Mountain works vapor mitts. I no longer do any cross-country skiing, but I can attest to the effective of vapor barrier. I would have loved to have those vapor mitts back when I was spending a lot of time outdoors in cold weather.
The problem with a separate vapor barrier is the hassle factor. I have read people suggest using a liner glove (to keep from freezing to metal when you take your mitts off), then a vapor barrier glove, then mittens. This sounds incredibly cumbersome compared to the vapor mitts solution.
Again, imagine you have a base layer, then a vapor barrier shirt, then a down vest, then a down jacket, then a waterproof jacket. Under exertion, you might want to wear just the base layer and vest. But you can't do that because the down will get sweat soaked, especially the part against your back. So you have to wear the vapor barrier shirt. But that adds too much warmth. Maybe you could add a vapor barrier vest. Yet another layer, more weight, more futzing around trying to get things just right... Much simpler just to incorporate the vapor barrier into the down vest and down jackets, and also add goretex outer shells to these garments. If the goretex outer shell is seam-sealed, then you reduce to: base layer, vest, jacket. Simple and goof-proof.