I find the Last Alliance spell an extremely iconic spell, also because it's wholly fashioned on the legendary prologue of the LOTR cinematographic trilogy. I think it would be a great loss for the faction, were it not to be present anymore in Imladris. Everything of it (the heroes, the army and the Second-Age touch) is simply fascinating. Whereas, speaking about the White Council, this proposal was already rejected in the past: Imladris is set in the War of the Ring timeline and the presence of Saruman as the chief of the council is a quite tough aspect to cope with too.
Regarding the other suggestions of your post, it should be better if you were more specific about the changes you deem necessary for the faction. Hinting vaguely at possible options doesn't help much. A bit more details will strengthen your arguments and make them more understandable to other users.