I like the soup-in-a-bread-bowl and salad-in-a-tostada-bowl concept. While eating a bento box lunch a while ago at a local Japanese restaurant, it occurred to me that the bento box should be edible.
Not that any classy restaurant would stoop so low, but perhaps a seaweed sheet could be formed into a bento shape. Enjoy the contents of the meal, then eat the yummy, healthy dish underneath.
I love seaweed wrapped around a delicious hunk of Tuna, but I can't imaging munching away at an entire bento box made of the stuff. If the material is not tasty, then it should be at least bio-degradable.