Since posting this question, I've done some more research, and here's what I'm planning to do for my hydration system. Instead of a camelback or platypus or similar, I'm going to be taking the "Convertube," which is manufactured by Source Vagabond Systems (an Israeli company, actually, which means you get bonus points for using their equipment on the Israel Trail).
http://www.source-vagabond.com/hydration-convertube.html
This is similar to the other products above, but instead of using the floppy water sack, you use a regular bottle. In Israel, 1.5-2 liter bottles are ubiquitous, and very light-weight (and cheap, relative to a platy). Switching from one bottle to the next doesn't involve the usual routine of opening up the pack, digging through to find the water pouch, supporting it with one hand while trying to pour with the other, then re-assemble the pack. Rather, it's as straight forward as unscrewing the cap from the empty bottle and screwing it on to the new one.
This item, since it is made in Israel, is one of the few that I've found to be cheaper inside Israel than out. The going price at the usual shops (Rikoshet, LeMetayel, various bike shops) is 44 NIS, though if you go to the new central bus station in Rishon L'Tzion, you can get it for 39 NIS. Online in the US, it is $17 (64 NIS at today's rate).
For those new to the Hebrew language, the general title for these devices in Hebrew is "Shluker", since the slang word for a "sip" (as in, "give me a sip of your soda") is "shluk".