FOR GUILD WARS PURPOSES ONLY, I would say a dead guild is any that does not score any points or any guild that does not post at least 10% or so of the bracket’s mean score (excluding 0s and any significant outlier [meaning a guild that’s #1 in the bracket by twice or thrice as many points as #2; same if #2 is compared to #3]).
If those are two different categories, call them “dead” and “non-competitive,” respectively. Dead guilds drop to the bottom, Non-competitives just drop in the manner @ChunkyMono has suggested elsewhere: as quickly as outlaying high-performers rise.
I think this is too severe, but the reason this was pointed out was that, at the actual competitive brackets, it would be impossible to win that many people down. So their bracket is no longer appropriate if, say, their guild imploded from its spot on-high.
So for a guild climbing, they shouldn’t be penalized by being barred from competing. But if they can’t stack up with fewer people, they won’t move up anyway, if the score-percentage-to-the-mean system above were adopted. Because it is assumed that anything that qualifies as “dead” drops a lot, and non-competitives basically stay ~30ish brackets of where they are (not much of a difference if you’re not at the top, and no 4-person guild should be in the top 30, regardless of longevity).
I can honestly say I wouldn’t feel penalized if moved to the bottom with all other 0s in this case, and it’s coming from a guy that did build a guild from the bottom. U3 (Bracket 5ish) was Bloodred Revenges and at the bottom brackets for a long while before we even got half a roster. But I always registered for Wars and fought my battles, even if the guild scored fewer than 50k points overall.
Anyone who cares enough to progress would. If they don’t play, they’re registering for the paltry rewards only, which they will get either way.
The only problem I see with this is a guild that registers and forgets to play or is unable to play due to real life. Part of me is sympathetic to the possibility. A larger part of me thinks that not many brackets have been “lost” in that event and can be regained with some dedicated effort (and hopefully a roster that one real-life obstacle/tragedy can’t wipe out all contributions).
Longevity in the game shouldn’t matter as much as it currently does, but I think it should be weighted and not a clean slate every War. I might be biased, being at the top right now, but I don’t think it would be good for the game if an entirely new guild could form the night before Wars and then win Wars.
But should it take two years? I don’t think it should even take 1. But if 6 of my best people left, and 6 from four other top guilds all at once (man, that’d be a lot of GMs who screwed up on the keeping-people-pleased front 
), it would be a real bummer to be beaten by the mutineers without a chance to recover first. And that’s just at the top—I imagine there’s a lot of player-churn in the mid-level guilds. Recombinations should spring forward if mergers happen, because more players = more points, but not all the way to the top overnight, right? 3 months, then — thereabouts.
6 months or so to climb from the bottom to the top if the roster is as good as mine is now—30ish people going 30-0 on-color each war, would be my “fairest” estimation.
Let endgamers start from scratch if they want to, but don’t let them usurp their way to the top without a little bit of an effort-tax, I say. Especially since the possibility of this partial-disbanding and re-climbing would gum up the gears for all the actually new guilds’ (meaning those with basically no endgame-experience on the roster) climbing.
Thank you for taking the time to take the topic seriously despite the tone some have taken up. I for one appreciate the listening even if my ideas aren’t deemed adoptable, so long as it’s explained why they wouldn’t work, or why the team’s against them in principle.
And also sorry if I’m rambling. I’ve given this topic a lot of thoughts over the years and also have a hard time organizing all I want to say when I’m typing on mobile
For the Horde