I don't think it will ruin merchanting. Personally, if I was in the total opposite side of the world, I won't go running to Varrock just to buy something that I needed. That would be a waste of energy. Merchants will have a way of buying stock and then selling it in the remote areas of the world where skillers are training and may need food or feathers, or whatever they need. Those who just want to sell their stuff will have a place for it. I think it would be better than we think.