I have thought about this myself, and believe it should be possible to move a population over to having fewer seeds. Steve Thorn above looks to be on the right track, hopefully he'll tell us more about his strain (hint hint). Here are some reasons why I think this is a preferable trait...
-Fewer seeds are obviously easier to deal with when eating watermelon than a hundred seeds.
-You could easily
enough just go the entirely seedless route for ease of eating, but then you have no seeds to propagate future delicious watermelons.
-For me, I feel a strong urge to grow out all of the seed within a fruit, because I don't want to leave a potential cross untested. I know that's a personal thing with me, but if there were 30 large seeds rather than 100 small seeds, it would make it easier for me to grow out 100% of the seed without the fear of missing something special by leaving it in the seed jar.