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 NS membership by eluding the Necrovion hunters for some days.
The idea of a two-tiered system where earning membership by yourself is less valuable than just being invited seems very odd to me, as putting in the effort to do it yourself should ideally (in my estimation) be more difficult than just convincing somebody to invite you, and therefore offer more benefits, not less.
That being said, I'm not sure I like the idea of a non-invite takeover or disbandment. Disbanding an alliance should be very difficult, and alliances should always remember to clean up their membership rosters (especially during critical moments like a conflict) lest they fall to disenchanted members who feel an alliance isn't meeting its intended purpose anymore.
While I don't personally think one should be able to roleplay or gather their way into disbanding an alliance, I do think one could be able to perform a special group scattering ritual that is non-specific to any particular alliance, but that's an idea of its own and only tangentially related to this one.