Perhaps increasing the height and lateral camber of the bow canvas moulding to gradually increase lateral drainage (as well as increasing the enclosed bow volume) would be an alternative possibility to reduce run on of waves to the conventional splashguard. I doubt that there would be a huge penalty of wind resistance if it was slightly higher in the vicinity of bow seat's waist at the finish, unless there was an increased tendency for the increased bow moulding to get pushed sideways by sidewinds (and no doubt any boat builder who knows what they are doing would already have designed the hull shape at the bows to resist this).
I've been thinking about this as I row on open water all the time. I think you're right that increased volume and high deck camber is the way to go. We can learn a lot from the surfskis. Take a look at any of them- Epic, Huki, Fenn, Stellar, etc., they have really figured out the bow shape for dealing with big seas. There's lots of volume, a very highly cambered deck (just about as sharp on top as on the bottom), no splashguard at all at the***pit (would get in the way of paddling). They love the kind of conditions where our shells' low-volume, rather flat-decked bows are getting stuck underwater continually- especially surfing downwind. I watch them pass me in open-water races, and the rougher it gets, the more their advantage (in the Blackburn Challenge, in 2012 a surfski beat the fastest single sculler- a very strong open-water rower- and finished in under 2 1/2 hours, which no sculler has been able to do yet).
One of the best open-water rowers on the east coast, Rich Klajnscek, has taken a Van Dusen surfski/kayak hull called a Mohican and turned it into a rowing shell. It's only 21 ft long and beamier than the usual 24' open-water shells, but he has been doing extremely well with it in all conditions, and is very happy with it in really rough stuff. Apparently the higher bow is not a serious issue with respect to sidewind forces.
6. Coast Guard