Nice box but your going to have some issues exposing it to moisture.
It's going to have to have some form of feet or runners under it to keep it up off the floor.
A dead flat plywood "roof" like that is unlikly to hold up.
Unless you prime and seal that whole box with something tough like an enamel or epoxy paint I do not see it lasting outside.
I've seen many many people try making the own dock boxes, deck boxes, fire wood boxes to sit on the deck out of plywood before and all ended up with issues after a few years. The paint peels, the top curls or delaminiates.