Seen a lot of ideas here over the past few weeks and just wanted to give my seven cents about how I think the Avatar system should work.
1) A Clan/Solo should only be able to summon one Avatar every X days, summoning an Avatar starts a cooldown until the next Avatar can be summoned.
2) Avatars should have tiers, with the current Avatars being a top tier summon and their resources adjusted. A lower tier Avatar should be added that focuses on damaging players and high-end monsters.
3) Obviously, the Avatars need a balance to make them at least semi-equal in usefulness.
4) Going along with number one, if a Clan summon an Avatar for one god, the cooldown for the other god's Avatars should be double.
5) An Anti-Avatar should be added to the game, this Avatar when summoned will last X days and be largely invisible unless actively defending. Its sole purpose is to battle an attacking Avatar. The cooldown on summoning an Anti-Avatar should be 1/2 that or normal Avatars.
6) There needs to be a player crafted siege weapon specially ment to damage Avatars.
7)When we do get sorrcery there should be high end spells that either buff or debuff Avatars.