As I agree that allience trading is not the way to go knowing SG will ever implement it and as I have suggested before a site wide annomous trading store would be more appropriate and deminish the chances of abuse.
But here is another option towards the allience trading if it was ever to be considered.
Only allow 1 hero swap per member per month. Swap could be for equal star hero and same for mats.
This would minimise abuse, force players to go crazy with swapping anything and SG don’t lose out as swapping for 1 equal will give the opportunity for those with excess heros to exchange.
Any already leveled heros being swapped would be brought back down to basic status or not allowed to swap a hero that has started to be leveled.
I feel this could be a fair compromise