Why in V'zos Brachah, is Shimon not mentioned?
Except for Rashi that said he is included in Yehudah name because of the incident with Cozbi Bat Tzur.
Ibn Ezra on Devarim 33:6 suggests (in addition to Rashi’s explanation quoted in the question) that Moshe was following Ya’akov’s example, who blessed neither Shim’on nor Levi at the end of Bereishit. (Levi nevertheless received a blessing from Moshe in the merit of Aharon.)
Ramban on Devarim 33:6 writes that given that Moshe wanted to bless Ephraim and Menashe separately, one of the other tribes had to be left out, to ensure a total of twelve. Shim’on was the one omitted, because it was a small tribe and did not receive an expansive blessing from Ya’akov.