The easiest method to make a prop outfit to fit a smaller body in a cloth sim is to keyframe the scale dial in the timeline. Scale dials are not morphs, so they can be used during simulations.
This looks very cool - it automates the most tedious part, which is to pick the collision groups! ^____^
I'm in love with the texture on the main promo (the aqua tealy one with the bits of pink). Why do stuff always comes along when I cant afford it! def going on my wishlist.