I know what you mean about the batteries. So Okay is only 1.5 years old and I've alredy replaced the house bank. Mine came with sealed batteries, after two boiled on me, I'm now using regular deep cycle wet cells and I can check them every month or so. I feel the "80 amp" alternator that came with the boat not good enough, I'm switching to a high output one.
I'm also looking at watermakers, and perhaps this winter will be the time to do it. i have my eye on these: http://www.hrosystems.com/reverseosmosis/sec.html
The modular installation is nice, as is the lack of a high pressure pump.
My thought is if I can run a gen or the engine for 2-3 hrs a day and recharge batteries and refill H2O tanks at the same time then I'm in good shape.
Have you guys seen any generators installed in 43 or 43ds?