Would it be possible to have an assembly of Torah-true Rabbis who could all agree that someone should be granted Semicha of the kind granted by Yehudah Ben Bava, and that person could then pass it on to others, so that a modern Sanhedrin could be seated, perhaps in Yavneh or Tiberias, and lead the Jewish people?
Maimonides (Hilchot Sanhedrin 4,11) raises the possibility that if all the sages of Eretz Yisrael were to agree on renewing the semicha, this might be halachically valid. Nearly five hundred years ago the sages of Safed attempted to reinstate the semicha but encountered the resistance of the sages of Jerusalem, led by the Ralbach. Responsa of the time deal with the issue at length. A major practical obstacle is the difficulty in determining who are the sages who need to reach agreement and then having them reach agreement on someone who is qualified to receive the semicha. Expertise in some fields of Torah- like knowing the nature of idol-worship and its related practices- has been lost, and this is necessary in someone who receives this semicha. Our best preparation for renewing the Sanhedrin, therefore, is training Torah scholars who are expert in all fields of the Torah (Iggrot Hr'Iyah 402).