Not a bad idea, but I think the work involved in making a decent looking hatch is more than it would be to just drop the tank. Don't remove the gas tank straps, leave them on the tank and instead unbolt the straps from the frame (8 bolts per tank, easy to access) and drop it straight down, it takes about 20 minutes by yourself.
Your sending units won't fail that often to necessitate the need for a hatch (I hope haha)