in taipei and hong kong, there are shops that store winter clothes, such as fur coats and leather jackets, will this be an option in Singapore as well? I don't suppose the fur coats and nice leather jackets cost less than a birkin, so perhaps from a risk perspective, there is not much (be sure to check the liability part though of the contract!).
otherwise, yes, to prevent mould growth, i throw in a couple of dehumidifying packets as well as stuffing my bags with white towels (clean and fresh from the dryer) which will also help (otherwise, you can always get acid free tissues!)