There is a problem with bladders vs bottles. If you soft sided, flexible bladder bursts and you have no back up, you are out of luck. And I wouldn't trust duct tape.

The problem I've seen with coming from a backpacking background is tainted by my observations of backpackers, so please don't take this as anything but a generality. Their plan, if things go bad, is to get off the trail and get help or a place to hole up. If TSHTF, you frequently don't have that option. Most of them have no flexibility in their gear, they plan for X days and Y conditions, and they they have XY gear.