As one of the realm's foremost alliance disbandment experts, I very much approve of this idea for its capability to revive alliances. For resource-based guilds, as many have stated already, a skill requirement makes a lot of sense. For traditional, more roleplaying, alliances a land loyalty (again as many have stated) and roleplaying requirement seems to be a suitable. For example I could see someone earning SoE membership by writing an interesting research paper, or earning military-focused alliance (KoB, GG) membership by challenging a gauntlet of enemies to prove yourself, or earning TW or