My solution was to use a fanny pack with water bottle holsters on each side. The whole idea falls apart– you might as well have a larger, heavier pack. It does move the heavier junk out of the should pack and onto your hips though.
This is the sort of water bottle carrier I had in mind. It is an REI model at 9oz.

There are all kinds of these things on the market as well as ones that hold smaller bladders with a hose.
The new Vaude Rock Ultralight 25 pack solves the problem.

It is just a couple ounces more than the REI Flash at 12.7oz/360g, but has mesh side pockets for bottles or you can hang a 2 liter bladder from the hook inside and it has an exit port on the RH side for the drinking tube. It will handle up to 15 pounds, so you really might pull off an August overnighter. I made up this example that could still be trimmed here and there:
Weight Item
1.10 bandana
9.00 Cirrus insulated vest
5.80 Lite-Speed windshirt
2.00 skull cap
3.80 Ulitmax Outdoor Scrambler socks
3.80 Beercan Stove
2.00 fuel tabs
0.35 spork
1.20 Titanium mug
1.10 Aqua Mira clorine dioxide
1.00 Bug Juice
0.80 Swiss Army Classic knife
6.70 first aid kit
1.10 Guide 426 compass
0.90 lighter and duct tape
1.50 maps
2.00 matches and candles in case
0.20 Microlite mini flashlight
2.00 Bolle PC sunglasses
4.00 personal hygiene kit
2.00 reading glasses
2.30 50' seine twine (bear rope, etc)
1.80 Space blanket
1.50 spare AAA batteries
1.00 sunscreen
1.80 Tracer headlamp
0.20 whistle
32.0 2 days food
64.0 H2O (2 liters)
1.20 1 liter Platypus in side pockets (2), one with sport cap
1.50 hand sanitizer
0.90 Snow stake digging tool
1.10 toilet paper
0.40 waterproof carry sack
12.7 Vaude Rock 25 pack
0.40 stuff sack for tent gear and rope
1.40 UltraSil dry sack (clothes and sleeping bag)
11.0 Gatewood Cape shelter/raingear
4.10 Spinnsheet ground cloth
1.36 titanium stakes
4.20 trimmed closed-cell pad
0.85 inflatable pillow
22.0 Micron XTS sleeping bag (50F)
220.06 Total ounces
13.75 Total pounds
That is a real world pack load too– water, fuel and food and nothing in my pockets. It assumes I am wearing a Capilene tee, hat, zip-off pants, briefs and socks. The compass, knife, match case, whistle, and flashlight could all go in my pockets. I normally wear the sunglasses and my first aid kit is on the heavy side (which I can live with if you don’t mind the pun). If I went to a 2000CI pack I could go three season with a 32F sleeping bag, gloves and some long underwear. The weight gain would be about 3 pounds given a slightly heavier pack and the gear.