You have also not taken care of the important case that the ON switch should be in the direct force path to make power be ON. That means that the ON control state should come from the same side of the latch that the switch feeds. If you need the opposite logic level for ON then feed the forced side of the latch with another gate from the package as an inverter. This is important becasue if the MCU crashes or goes to sleep in the OFF control active state it is not possible to power the system back on.

Also as Erik has pointed out you have lost the bias toward forcing the latch into the OFF state when installing a battery. While this is not a really necessary feature it is kind of nice for the little system to come up in OFF when a battery is first installed. (This behavior also allows a momentary battery interruption to be a way to turn the gadget off when software is not yet in place to do the OFF control logic.

- Michael Karas