A bracha (blessing) is not only a wish for good things to happen. We see with the blessings of Yaakov in Vayechi that Rav Hirsch explains that they describe the mission and capabilities of the person being blessed.
Rav Hirsch shows that the first four brachos analyze the characters of the four oldest sons and use them to determine who should become the melech of the up coming namtion. The remaining brachos also show the characters of the shvatim and how they will fit into the nation that will be.
At the end of all the brachos Rav Hirsch says on Vayechi 49:28
All these are the twelve tribes of Israel, and this is what their
father spoke to them and blessed them; each man, according to his
blessing, he blessed them.
As Rav Hirsch comments:
... and this - it is not the blessing that Jacob gave to his children,
for it is partly only description of their characteristics - but it is
what their father said (דבר להם) about them, how he described each one
in their special characteristics when he blessed them. But, "with a
blessing in accordance with their specialties" did he thereupon bless
them. After he proclaimed the specialty of each one of them, he
blessed him accordingly, that in his specialty and by and with that
specialty he should find blessing i.e. happiness and satisfaction.
that is why it says, each one according to his blessing, he blessed
them, not him אותו, but all of them אותם "each one participated in a general blessing, and the special blessing of each one was for the
benefit of all.
Here he has described the mission of each son and what he will contribute to the whole.
Rav Hirsch also makes clear that Toldos 27:29 that the blessing will apply only if Eisav fulfills the mission by translating the end of that verse as
People will serve the and natons bow down to thee - Be a Man to thy
brethren so that thy mother's sons bow down to the, Then whoso
curseth thee will be cursed and whoso blesseth thee will be blessed.
Rav Hirsch explains this way of taking the pasuk as:
By the material prosperity which Hashem will grant you, nations and
states will bow down before you, but seek to compete with your brother
Jacob to obtain the spiritual greatness also, so that not only
strangers but the sons of your mother bow down before you that you
stand before them as a "man", then if you achieve this, then
אורריך אאור ומברכיך ברוך.
In this case, Yitzchak was setting out the mission of the son who would be dealing with the outside world and fighting off the yetzer Hara. That is why the blessing is framed in physical terms that only applied after the Israelites conquered Canaan. Until then they were shepherds as shown by the gifts Yaakov sent to Eisav.
Rav Hirsch then explains Toldos 27:33
similar to Rashi.
He, too, shall be blessed: That you should not say that had Jacob not deceived his father, he would not have received the blessings.
Therefore, he concurred and blessed him intentionally (Gen. Rabbah
As Rav Hirsch says:
For now it had become clear to him, how everyone in the Abrahamitic
nation, everything and everybody, soldiers, merchants etc. too, have
to be filled with the Abrahamitic spirit. So that he no longer saw any
position in the House of Abraham for Esau.
Since Rav Hirsch says that it was connected to the mission, Yaakov had to take on the mission to get the bracha.
We see from the explanation of ארור in Noach 9:25 as the opposite of ברוך that a similar principle apples.