IMHO, "neutral" should be the largest slice, with the other two roughly balanced.
Unfortunately (as I said on the other thread), I don't think this is realistic. The players have shown, through the decade+ of BM's history, that they
will seek out peaceful relations or alliances with other realms, even ones on the other side of the continent who they have next to no chance of ever meeting in person.
And frankly, unless we can come up with some
really, really good game mechanics to encourage neutrality and discourage many peace treaties and alliances, I think this is likely to be one of those instances where we just have to accept that that's the way human nature is going to push, and let it be that way, rather than trying to force the playerbase to play in a way that
we think is "right".