On the Shabbos before Purim, my rav shared a very interesting thought, which started me thinking.
When Mordechai refused to bow down to Haman, the sages of his time challenged him. They asked why he was putting himself and the Jewish people in danger, and said that we have a precedent from Yakov Avinu - he and all of his family bowed down in front of Esav. Certainly one can bow down in front of Esav's progeny, Haman!
To this Mordechai responded and said that while it was true that all of their ancestors bowed down, his own ancestor, Binyomin, was not yet born and was the only tribe that did not prostrate in front of Esav. Mordechai therefore explained that he had his own precedent to follow.
Another interesting thought that I have seen is that it was Shaul, who was a descendant of Binyomin, who was sent on the mission to destroy Amalek, the grandson of Esav who represents all of the evil in the world. Mordechai, a descendant of Binyomin would be the vehicle for the downfall of Amalek's descendant Haman.
It is also worthy of noting that our sages tell us that Yosef was originally supposed to have twelve tribes, similar to Yakov. However, due to a sin, ten of the twelve were given to Binyomin. Each of Binyomin's ten sons were named after Yosef in some way (as Rashi notes).
Also interesting to note is that just as we find the concept of the connection between Moshiach ben Yosef and Moshiach ben Dovid, there is also a clear connection between Yehuda (מב"ד) and Binyomin (perhaps מב"י?) that is worthy of explanation. In fact, Shaul was supposed to have been the Moshiach ben Yosef for Dovid as Moshiach ben Dovid, if not for the fact that he ended up being unworthy.
I was told that while we do indeed find that Moshiach ben Dovid must be from the physical lineage of Dovid Hamelech, there does not seem to be a source stating that Moshiach ben Yosef must actually be from Yosef. This is actually quite an important point, because there are opinions that the tribes of Ephraim and Menashe were both lost to Klal Yisrael, so if it was necessary for MBY to be from either of those two tribes, we might find ourselves in a quandary. In any event, the tribe of Binyomin still exists as a significant part of Klal Yisrael, as the Jewish people today are composed of what was the kingdom of Judah, which consisted of the tribes of Yehuda, Binyomin and some Leviim and Kohanim.
It is also significant to note that the Beis Hamikdash was located on the border between Yehuda and Binyomin's portions in Eretz Yisroel, indicating a spiritual partnership between the two in being the vehicle for bringing Hashem's Divine Presence into the world.
Something else that comes to mind is that Binyomin was blessed by Yosef with the bracha of חן - grace, which Rebbe Nachman explains is the power of Torah and Tefillah (prayer) that bring about Hashem's response. These are the very tools that Moshiach will use to bring the world to its ultimate rectification.