Perhaps...

this can help us understand one of the more troublesome questions that we encounter when learning through the early part of the Torah.  Throughout ספר בראשית, and even into שמות, a consistently find within families that the younger brother outdoes the older one.  With one important exception, we always find the בכור on the scrapheap of history, while the younger brother is the one who shines.  Maybe the lesson to be learned is that although we are Hashem's בכור, that presents a duty, but the privileges that come along with it are merit based, and "birth order" guarantees nothing.  By building His "first-born" nation on the foundation of younger siblings who won out over their own first-born, Hashem communicates to us that the position is a default setting, but that we have to be worthy of that status to earn it.  Maybe we can say something similar (maybe others already do?) about the odd unions that lead to the Jewish leadership - Yaakov & Leah, Yehuda & Tamar, Lot & his daughter, Ruth & Boaz etc.  We know halachikally that a ממזר תלמיד חכם takes precedence over a כהן גדול עם הארץ.  Again, the message seems to be that despite our glorious yichus as the children of the אבות and אמהות, this type of global leadership is distributed based on merit, not legacy.  We should keep it in mind as we head into next week's פרשה with the story of מכת בכורות, and the mitzva of פדיון בכור.

This is not to say that our very chosenness is variable, and subject to exchange or return when the product (us) is defective.  This is a bigger issue that is probably better dealt with within the Jewish Philosophy classes, but that is the message of the ברית בין הבתרים, as those of you who have heard my shiur on the subject no doubt remember.