The Haggarian Connection

In Parshas Chayei Sara we are taught that Avraham sent his son Yitzchok to fetch Haggar and bring her back to Avraham. It trikes me initially as a bit strange that Avraham would send Yitzchok, of all people, to do this task. After all the relationship between Haggar and Yitchok's mother was not a good one, and Yitzchok had not a good experience with Haggar's son Yishmael, either.
On looking a little deeper there is an interesting connection between the two. Both Yitzchok and Haggar have the Gematria (numerical value) of 208. While our Sages point out that this is eight times the Gematria of God's name, there may be another connection as well.
When Sara realized that she could not give birth she suggested to Avraham that he take Haggar for a wife, "Perhaps I can build a family through her." I want to suggest that Sara sensed that within Haggar there was the same trait of Gevurah that Yitzchok possessed (hence the same numerical value). Through prophecy Sara knew that she was destined to have a child with this trait. When she saw that she was not capable to having the child herself, she assumed that Haggar, who possessed the same trait, was meant to be the surrogate mother.
And, indeed, Haggar, by giving birth to Yishmael, did show that she had the ability to bring forth a child with the trait of Gevurah. Unfortunately, Yishmael chose to use it for evil rather than good. This is why what so upset Sarah about Yishmael was that she saw him מצחק. Rav Moshe Dovid Valle explains this to mean that she saw he was Yitzchok-like. Unfortunately in a bad way, not a good one. However, because he was so similar to Yitzchok she insisted that Avrohom banish him as she feared that that similarity might lead to Yitzchok emulating the path of Yishmael.