Ymb,
1. Where does the Maharal say that? That is truly amazing as only the big three are yehareg uval yaavor. In any case, in Chiddushei Agadot on the Gemara he says explicitly that all three are the kiyum of the Galut.
2. There is much that you are missing.Obviusly Rav Meir Simcha is talking about a forcible aliya before the time like Ephraim. However, being that the other nations agreed that is a sign that it is not before the time (and certainly not by force) it is not the case so we do not need a navi.