It is already possible to transfer items from one faction to another with neutral auction houses. Not putting it in the legacy system will only be a inconvenience for those who really want to move items between factions. If you don't have any friend to help you you can always get a second account. On my old wow server this was completely broken, I get an image in my head of people playing the market, moving items from one side to the other to sell at a profit. Blizzard did not care about this, probably because it meant they got double the subscription fee from some people.