Yankel berel, sorry, but your “perforces” don’t work. Rashi himself has two explanations re Daniel, and he himself does not say which he prefers. The Ramban may very well have held of the one that says that Mashiach will be similar to Daniel. He had no reason to worry that the King of Seville would argue based on the other pshat.
Also, you say that the Ramban always tells us when he disagrees with Rashi. Is that true? Have you researched all of Shas to come up with that statement? Furthermore, does your “rule” apply in aggadata?