I like your idea but I take it one or two steps further to simplify. I just use rubber bands. That way all you need is an empty frame and some rubber bands. No string, nails, or preassembly required. You just put the rubber bands around the frame vertically. You can use as many or as few as you need. The bees will chew them out but not until they have attached the comb securely to the frame.
\"The man who sets out to carry a cat by its tail learns something that will always be useful and which never will grow dim or doubtful.\" - Mark Twain