I would definitely NOT use any plastic boxes for storage of shoes or handbags- the leather goods are meant to breath, plastic is not ensuring that important ventilation. Only cardboard or wooden box is good enough for an expensive bag, but then is it not clear...
My solution is to fill the bags itself by some lightweight, brand new, clean, things (like a new jumper or a cotton fluffy towel (if not heavy) wrapped in a tender thin plastic bag) to keep shape, then put it on the shelf in the wardrobe or a closet, or to put the bag into its dustbag, then its paper shop-given bag and hang that bag by the rope handles on a hanger on a rail inside the wardrobe, so the Mulberry itself does not experience any pressure, but sits in its paper home, and is saves space at the bottom shelf of the wardrobe...
My husband comes and asks... "what shall I wear to such and such... for a change" I would say - have a look in my Mulberry bags...
If I keep only paper inside the bags, it is not fair on space... at the end of the day the bag is a container... should fulfil its purpose even when sitting in its dustbag...