I think it's a good idea to add more to the water areas, as at the moment, unless you build down into them (like in Waterworld), there's not much point to the large water areas.

The only problem I can see with bigger boats, is that on a server level it would have to track far more objects moving about, whether in use or not. For single player or closed multiplayer servers, I reckon this would be good fun - but with the number of members CFUK have, it could get a bit messy lol :S