HD ~ I did a lot of thinking on what you said. I believe you are right about most of it but wrong about the win-win situation. I agree I had false hopes and I most certainly came at this the wrong way. I failed to take my children's point of view into account. So here is what I think my solution should be. I welcome all opinions before I implement this into my family this weekend.
First of all I can see how my children would resent having to suddenly subject themselves to someone they barely knew. Their father abandoned them so why listen to another "father" or trust them? He says he'll never leave but then so did their dad. I should have came at that a different way. So here is what I am going to do.
I made a list of all the major behavioral issues that my children have and set guidelines for discipline when those behaviors are exhibited. This weekend (after talking to my husband privately first) I am going to give these guidelines to my kids verbally and then post them on our fridge. The rules and consequences are there in black and white. Also, I am going to inform them that my h has full rights to enforce these rules that I set as their parent. This still gives my h room to be the authority figure within guidelines that I myself have set. It also tells my children whining to mom will do no good as the punishments were decided by me to begin with. Creating solidarity in the parenting plan that is terribly lacking now since we always disagree about punishment although never in front of the children. That seems win-win to me. Granted he won't like it but it's better than totally losing face and authority. Gives opportunity instead of restriction.
It won't stop his unrealistic behavior at the time of his blow up but it will give him a structured opportunity to renegotiate and take the instability out of it for my kids. They will simply have to "wait" for their real punishment to be given when he cools down. Might also take some of the pressure off him?
Thoughts? Opinions? Suggestions?
I think your plan is good, but I also think you have to accept a significant possibility that your husband may not go along with it (or any other plan you devise) long term. If this is this is the case (what I meant by "no win-win situation", you are going to have to choose:
1. Empower your husband's BPD-induced punishments at the expense of your daughters' mental well being, or
2. Anger your husband by making yourself the final authority on discipline, but protect your daughters from his wrath
To me the decision is easy because in both cases, the pwBPD is dysregulated which is par for the course while the daughters clearly benefit from the 2nd choice.
I hope you do find a win-win situation. I also hope you make an "if all else fails" choice that benefits your entire family best.
BTW, I've made this choice already in preparation of my BPDw ever reaching the stage your husband has towards our own 3 young daughters. It's a bit more difficult as she's their biological mother, but I'm not going to let her screw up their heads (like her parents did hers which I think is a big reason she has BPD).