Its probably a good thing to do but have to remember one thing, that whatever gets by one of the seals, whether it be coolant or oil, must be able to leave that chamber and not build up against the other seal. So, it can not run up above that seals. And as was pointed out, mud and other stuff should not be allowed to enter the area either.
Here's a thought... and one I may go with as mine also has no tube on it. My Brute Force also has a system like this but it also has a tube on it. It does drop straight down to the skid plate to drain but Kawasaki put a small flapper check valve on the end of the tube so when under water, it closes against the water pressure and seals it from anything running back up the tube. Anyone can buy those little check valve from any Kawie parts house.