The basic hatch design sounds like it will work.
While I have heard of using magnets, I have never used them to hold anything onto one of my airplanes, so I don't know if that part of the design is a good solution or not.
If I recall correctly my fuel tank foam presses against the section that will be your hatch, those magnets would have to be really strong for me to trust them.
I am a screw the hatch on kind of guy and do not find the appearence of the screws to be offensive, in fact if the screws are small and well placed I think they are an enhancement.
My H.B. was built without a hatch so this is just conversation.