Agh. Too many posts to reply to in order. couple things though:
Electric in tank heaters will be the most energy efficient way to heat the tank. If you are going to use electricity, there is no way to do it more economically than this. So if efficiency is your goal, the electric THWH is a waste of time. I can go into detail on that point if you like.
The only reason I see for running a more complex system is to make use of the natural gas, which is a good enough reason. How much does natural gas cost compared to electricity there? If it's less than a factor of 2, you may be shooting yourself in the foot... I can go into detail on that too if you want, but first let's hear the numbers.
The first rule of engineering is not that simpler is better by the way, to whomever said that (Although I'm not contending that simpler is often better). The first rule of engineering is to always clearly understand the problem, and sometimes it trumps the KISS rule. If the simplest solution is also the most expensive or least effective it isn't really the 'best' solution.