Jeremy's Plan is a way to show he is just as bad as they are now
I think maybe this is to show how even the people who thought evil of what they were doing behind closed doors, can transform by their own desire or personal need ( Jer loves Rachel...sees how hurt and scared she is and would do anything to not see her in pain) and so in a MOMENT all of our morals could be tested.
Its hard to live this moralistic life where you go "oh well... there is nothing we can do to make this go our way so thats it its over" without wanting to do something desperate to get it to how you want.
In a weird way this show reminds me of breaking bad ..... showing how a good hearted person with morals can slowly transform after they drink the coolaid and they just get more bad and more bad.
I have a cold so if this doesn't make sense I blame it on that :)