Switching a line of batteries with MOSFETs
I'm not sure what you are asking for. From the schematics it looks like a series connection of 2 batteries. If you open the loop at some point the load will not see any voltage.

About the mosfet, you need to guarantee that its driver is powered in every condition (also with mosfet open, otherwise you can't close it anymore). Then, this is a high side mosfet so you have to drive it correctly. Usually, for this kind of thing it is easier to use N-Mos and switch the negative pole.