Maybe a somewhat radical idea and would certainly change the way RR is going.
How about a crusade option. Kings could leave their alliance and go on crusades, they would have all alliance non war boosts by default (these could cost minimal gold to maintain and strength could be level dependant) these kings can only fight other crusading kings. The individual leaderboard could be dedicated to only crusading (non allied kings) with the alliance leaderboard being there just for alliances, as that bits all about the team.
One of the current problems with RR is that it has become far too focused on alliances, consequently many who want to play it as a solo game are leaving because they can’t compete without being in an alliance and all the extra issues that can bring with it, additionally many higher level kings are leaving as they are getting frustrated by costs of wars, introduction of skull bonuses, cof skulls and the commitment required every five days.
By bringing in this option you are giving people the chance to play the game and compete in two different ways, in a team or solo. Kings can, during the non war season, either leave to go on a crusade or as an alternative come back from a crusade and join an alliance, my guess many will never return! There can be no shifting in between mid season, to help maintain the alliance balance. Also an added positive side effect it would effectively eliminate full alliances strip/dumping on the leaderboards,
I think given this option a significant amount of players who are currently “tied” to an alliance would leave and enjoy the game as it once was, as single players again, even if it was for rest period.