Go for it - my plot looks like Blue Peter larging it - every bed has some structure or another. 0oh what fun I have with hazel, twine, bamboo and willow. Of course, not all of these are successful - the polytunnel top blew away last year leaving me with a sort of open top box (but the tomatoes were still fantastic). Your idea sounds both aesthetically interesting and structurally sound. However, be warned, it can be addictive. Good Luck