Yeah, right with this guy, definitely splash resistant, make it easy to get your camera out quickly, and make it understated and classy so it doesn't look like a camera bag so it's less of a target for thieves. Maybe tripod straps?
Also this is going to sound lame but a good camera fanny pack would be the greatest thing ever, seriously. I have been using a hunting one this year and it has been the single greatest factor to help me shoot skiing. Make it splash resistant, make it have a flap over the top, padded, maybe semi stiff sides? Have it be able to fit one DSLR with a lens, and one other lens, put straps on the bottom for a tripod/glidecam, make the strap buckle on the right side of the bag, not on the opposite side, basically so that it can be worn with the bag part over your belly. Have a slim front pocket for accessories, and some little organizer pockets as well, make the zippers heavy duty and large so they can be used with gloves. Seriously, fanny packs are the best thing for shooting skiing ever.