It does suck when my fully charged iPhone has been sitting on my desk at work all day and I haven't even touched it and then the battery is dead before I get home, I feel like it kind of sucks to not have a phone in case of an emergency for the most risky part of the day: the late night commute home. But of all the features a smartphone has, the ability to make a call is probably the one that can save your life. I think that one feature should be preserved at all costs.
A great solution would be to simply duct tape an old Nokia to the back of your smartphone, that way no matter what, you can always have a working phone with you.
Ahh... I miss the days of just charging your phone twice a month and not giving a damn about when your battery will die. I think the most important thing would be to get back to that level of battery life, and not just introduce more features that only make battery drain worse. It would be hugely important to make sure that your phone will work for 24 hours, no matter what. There are times when you're stuck somewhere and need help, and those are usually the times when you've been away from a charger for too long. So the times when you need your phone the most are the times you're the least likely to be able to use it...