Why Bless Esav?

Introduction

Parental Favoritism

From the very opening of the Yaakov and Esav narratives, the brothers are pitted one against each other, not least by their parents themselves.  Shortly after recording their births, the text points out:

This parental disagreement comes to the fore in Chapter 27, the story of the blessings.  While Yitzchak hoped to bless Esav, Rivka used her wiles to ensure that the blessing went instead to Yaakov.  What, though, led to each parent's decision?  Was each motivated only by personal preference? Were not other factors, such as personal character, worthiness, or birth order taken into account? 

What Did Hashem Say?

Two incidents in Chapter 25 raise further issues regarding the choice of the blessings' recipient.  After Rivka questions the cause of her abnormal fetal movement, she receives a prophecy about her future children:

Rivka is apparently told, even before the birth of her twins, that the elder would serve the younger.  If so, should it not have been evident that Hashem's choice was Yaakov?  How could Yitzchak act against a prophecy?  Did Rivka never share it with her husband? If not, why did she keep such information to herself?  Or, is it possible that bestowing the blessing on Esav was actually not contradicting the prophecy?

Buying the Birthright, Buying the Blessings?

Later in Chapter 25, the text relays how Esav sells his birthright to Yaakov:

Regardless of how one evaluates the actions of either brother during this sale, it would seem that, in the end, Yaakov could claim the birthright as his own.  Did this earn him rights to the blessings as well?  Was the sale known to either parent, and, if so, did it have any effect on their actions?