Looking at the rewards, this is what I would probably do…
For the record, I’m just thinking out loud here, because it’s fun stuff.
The top 100 (top 10 brackets) use the system as proposed above, as it sounds good.
Below the top 100, you have already defined bracket groups: 100-199, 200-399, 400-499. 1000+. You could use those, or make groups of 100. And then rank all the guilds in those group by score, and the top x% (for example 10%) move up one group, the bottom x% move down one group.
The tricky point of course is the flow from “low” groups to bracket 10.
PS, if you wanted to make it “more effort” to get into the top 10, you could have the top 15 or 20 use the proposed system, and then below that use the groups. That would prolong the time of being able to hit bracket 1 by 5 to 10 weeks…
But I honestly don’t think you should. A clean new guild now has the disadvantage of low bonus multiplier, so it would have to work hard. Let’s say you use groups of 100, and the new guild starts in group 500-600.
It would take them probably 4 weeks to move up to group 100-200.
Since the top 10% can’t move up anymore, but more like the top 5%, it might already be harder to get to the top 100, but lets say they do, 5 weeks total.
Now they have to win in each bracket, to move up 2 spots, so 4 more weeks to hit bracket 3 (9 weeks total).
Now finish in the top for 2 weeks, and we have 11 weeks, it would take you to hit bracket 1.
If that’s even possible, as those high brackets are filled with guilds that have (close to) 50% bonus score for troops, where as in 11 weeks, I doubt you have more then 30% bonus.
So best case scenario it would take a new guild 3 months time to get to the top.
Seems fine to me… 3 months is a long time