I think that this will only work well if you're growing corn and beans that you intend to harvest at the mature dry stage -- like corn to grind into cornmeal (or maybe popcorn?), and beans that you want to harvest the dry beans for cooking with. Everything should essentially be ready to harvest at the same time then, at the end of the season. (I too tried doing sweet corn and string beans, along with pumpkins, years ago -- which was a huge mess and impossible to harvest; since then I've thought about it and came to the above conclusion)
