I like idea and wanted to offer something like this, but not spliting by week, because all wants to play, waiting few weeks for war it’s too much.
Let all leagues are run togehter and let the alliance leader choose in which league will his alliance take a part. And the players can’t use heroes, which are higher than league status.
3-stars league: only 1, 2 and 3 stars heroes;
4-stars – 1, 2, 3 and 4 stars heroes;
and Champions League – any heroes.
And there is a space for different special tournaments. Game can offer from time to time the special war (additional to 3 leagues): color battle or magical battle, and alliances, which sign up in this kind of tournament will have to use only that heroes.
For example: Green month (only nature heroes) or Magic month (only druids, mages and sorcerers).
But because it’s to hard to have 30 green heroes, this special battles may have special rules, for example, 2-3 times for attack by one hero.