I don't understand why all the restrictions against multitasking. I think the better approach would be to limit the amount of programs able to run to an arbitrary number, say 3. When you want to open program 4, the OS asks you to double tap a program to close first.
I think a better option is to let the user run as many programs as they want. If they want to run multiple applications at once, then they should be able to. Maybe they believe the battery life hit is worth it. I don't think anyone on here would be happy if Windows would tell you that you can't open more applications because it would use more battery on your laptop.