Wasting water waiting for hot water???

At our previous two S&B's, I installed smaller water heaters at each point of use, rather than one large one when I built them. Every hot faucet had hot water within a couple of seconds at most. I'm currently determining the feasibility of adding a second 6 gallon heater under the bathroom sink in our coach. The existing heater is just a few feet from the kitchen sink, but a 10' or so pipe run from the bathroom. The second heater would be fed from the existing heater, giving us both "instant" hot water in the bathroom, as well as doubling the capacity when we have full hookups where water usage and waste capacity are not issues.