If the plan was to have Yaakov get the bchor for just some soup, why didn’t Yaakov get the bchor in the 1st place?
Rashi on Hoshea 12:4:
‘In the womb, he seized his brother’s heel: All this I did for him, he held him by the heel, as a sign that he would be a master over him.’
It thus follows that the order of birth was, in the first instance, for the sake of a sign.
The Sforno on Beresheit 25:24:
‘“Behold there were twins in her womb.” Those who were assisting with the birth recognised, even before the actual birth, that twins were being delivered, and when the first to be born proved to be covered as with a hairy mantle, they realised that his birth should have been more difficult and later than that of the smooth one, therefore they called his name עשו (Esau) (as though to say) his brother did it by forcing him out first (עשו related to עשוי, I.e. the efforts exerted by the other infant forced him out).’
And on Beresheit 25:26:
‘“So he named him (lit., called his name) Jacob.” (From the root עקב, ‘the end’, I.e. he will remain at the end.) This was indicated by the fact that his hand held on to his brother’s heel. Our Sages tell us that G-d gave him this name (Jacob) to show that he will survive after the destruction of all the nations, as it is written [in Yermiyahu 46:28].’
We thus might conclude from this that the order of birth was for the sake of the names they would be given (it is said somewhere, I forget where, that names influence character).
Hope that helps.
P.S. If someone could edit the formatting on this I would be grateful (I haven’t quite mastered that yet).
The story of Esav and Ya'akov may be a conflation of a personal story and a representation of the point in human history where we had to place our bets on argriculture rather than hunting.
Hunting came first, but we needed to move on to agriculture and civilization in order to thrive.
I feel like the whole family, including Esav, either expected or had planned that this was going to happen. Yitzchak's wilful ignorance / self-deception is given away by the fact that he consciously recognizes Yaakov's voice, but he lets himself "be led astray" by a single piece of weak evidence because deep down he knows that his taste for meat is not as important as his concern for the welfare of his future generations (kind of like us right now, history does tend to repeat itself).
There's still a pretense at following the tradition of blessing the first born - humans may be highly adaptable, but for the most part don't like change - but his heart's clearly not in it.