Just gonna throw this out there: people were also upset about the copperhead change, I think it's important to go open into this with an open mind. This change could be a good thing.
As far as I'm concerned, non sf / patron legendaries should only be tradeable for another unique legendary. Legendary duplicates should also not be tradeable to expand your collection (eg: can't trade your second JSB). With clothes, I think trading is even more welcome, since looting all the garb you might want can be very time consuming and even then, you may not get items you want. Not sure if there are drop rates for clothes, but for cross gender trading, there should just be an equivalency system (obviously your male pirate isn't gonna wear a corset, so that corset turns into an embellished vest or something similar, with the same color applied to the item) Beyond that, I don't see any extra caveats that pop into my head. If players wish to gift non legendary items to each other I think it should be allowed.