That sort of makes it a bit more complicated as with two sperate latching switches you could have 'em both on at the same this may or may not be a Good Thing. The center off switch avoids that possibilty.
Perhaps getting a decent IP65 enclosure and mounting it in a sheltered position is the best bet. Trouble is with the flippy lid, the owners will not always make sure it is fully closed... and make sure there is a small drain hole for condensation to get out through as well.