Condensation occurs when the incoming water is very cold and the room temperature is fairly high. I have not heard of anyone trying what you propose, but it will probably work. The extra length of pipe will give the water time to temper. Another thought is if you have not been using low flow toilets and are now switching to low flow, condensation is not as much of a problem with low flow because only approximately half of the tank of water is used per flush. The remaining water has had a chance to warm and the incoming cold water mixes with this remaining water so it is not as cold. And, the water that is used to refill has already had a chance to warm somewhat. Your scheme would give even more of an opportunity for this water to warm.