The only way I can think of to deal with the water weight is to stock up on freeze-dried water.

I agree with Jim: you have to take the right gear to handle the expected conditions and activities. I'd go a step further, though: don't take anything more than that gear. (I'm also 60, probably not in as good a shape as you, same weight and build, and also a big fan of the Megalite.)

The first round of weight reduction (to make room for that 8 - 12 pounds of water you'll carry) is to get rid of anything that's not necessary. That little deck of miniature cards, that spare T-shirt, the just-in-case fleece, iPod, stuff sacks for your clothes and sleeping bags, spare headlamp, beverage mixes - and the teapot to boil the water and the mug to drink them from: leave those behind. Let your rain jacket double as your windbreaker, and your rain pants double as you long pants. I did all of that once, when every ounce counted. The stuff sacks were 4 ounces, the beverages were 12 ounces, and the spare pot/mug was another 8 ounces - total was a pound and a half, which almost equaled one of thos liters of water. Carrying 6 liters of water and food for 4 days, my total starting weight was only 28 pounds.

So, once you know what your minimum gear requirements are, your next goal is to get the lightest versions of everything you need. (You might look at a Silshelter instead of a rectangular tarp, to get an easy pitch and some weather protection - it's only a pound.) At this point, lightening your pack also lightens your wallet, but it's worth it. Replace the fleece and synthetic jackets with 850-fill down, Nalgene bottles with Platypus (Platypii?), get a lighter water filter (or use chemicals), get titanium cookware (one pot, which you can do by minimizing your meal prep to freezer-bag cooking or freeze-dried entrees), and replace that Svea stove with a 3-oz. canister stove. Finally, make sure you're not carrying too much pack. There are packs available today that will carry 35 pound loads, but weigh only 3-4 pounds. I loved my old Dana Terraplane, but once I realized I would never again carry 30 pounds, I replaced it with a 3.5 pound pack that can handle 35 pounds (just in case I decide to do something crazy.)

I've also been looking at that next weight-reduction step: it may involve a Six Moon Designs pack and tent, an alcohol stove and titanium pot, and some sort of lighter self-inflating pad. I figure I can still lose 4 pounds or so if I have to - but for my typical trips, in the Eastern US, I haven't needed to get quite that radical yet, and can still avoid a few luxuries.

I'm getting ready to take a 4-day trip, and plan on taking winter clothing. There may be a spot where I need to carry 3 liters of water, but my load won't exceed 29 pounds, and will be closer to 25 most of the time.