Changing the ways in which sanctioned alliances are chosen would certainly add interest to the game, that's for sure. Something along the lines of what you proposed would add depth to the game, and open up new pathways for alliances as it would be possible to gain a sanction by something other than membership.
Perhaps select 4 by NS, then 6 by score, and 2 more in there for Avg. NS. I don't think it really makes sense to use both score and membership, since membership is the largest contributor to score in the first place.
A chance is needed though, regardless of what the change is. Hopefully it will not be something that simply addresses this instance, and instead actually solves the problem.