It is like being with someone else will never match the ex but it is either that or accept being alone. A dilemma, a real dilemma.
To be blunt, I see no dilemma here. Why would any of us want someone else who will ever match the things that our pwBPD did? The idealization was not real, and the devaluation was abusive. Why would anyone want that? Wouldn't it be better to have something real and not painful? What is inside that makes us so desperate for the high that we are willing to endure the painful crash?
That being said, I totally get the sadness and hurt from walking away from someone that you love so much. But, being in a r/s composed of unrequited love is far from healthy. It's also far from sustainable. I would think that we'd all want to give the love that we are capable of giving to someone who is going to reciprocate.