Why not use the Web to buy and sell transmission rights at prices derived from bids and offers?
You make an offer, I accept. You deliver a product, I deliver money. This simple construct works well in just about any industry you can name. When a willing buyer and seller negotiate a contract, each achieves an outcome he considers best. Moreover, each is obliged to meet the needs of the other - reliably. No central authority sets the price or allocates supply. We depend on markets for reliable production and delivery of other essential goods; why not for electricity?