Middle ground: Scrap the gold requirement on GWD instances and make it only payable from Deaths Coffer. This way, Irons have an incentive to not drop trade shit because they need to sacrifice duplicate pieces to the coffer to pay for instances.
No one can complain about irons dropping dupes anymore and irons get an actually decent way to pay for their instances that isn't dipping into another one of their scarce resources (GP).
It has been changed to offer the ability for all accounts to use deaths coffer to pay for all instances in the game, as a separate question.