I believe the only way we can retain an informal clan challenge system and avoid any future rating "boosting" techniques and potential collusion between a small number of clans is to employ a single clan rating that functions much the same way as a player rating.
The individual clan's members ratings are irrelevant, and play no part in the proposed rating system.
I have been prototyping an Elo system, modified to reflect the number of wins in a challenge. (Otherwise, a 1 vs 1 challenge win would award as many points as a 12 vs 12, for example)
Multiple challenge wins against a lowly placed clan results in very little movement.
A big multi-man challenge against a well rated clan can result in significant rating changes, (positive and negative for wins and losses, respectively) where as 1 vs. 1 challenges will often result in no rating change, or very little.
I would prefer there to be a weighting towards bigger challenges, where the risks to clan rating are more significant. Primarily to avoid the risk-averse clan leader creating multiple single man challenges, even when a bigger team is available.
So 10 "1 vs 1" challenges must not be equivalent to a single 1 "10 vs 10" challenge, with a preference for the latter.
Below I have linked a graph (Woodpushers Clan, in this example). Do not get distracted by their actual rating - this is just a prototype - but you will see that big wins (many games won) result in steep rating climbs, and vice versa.
Clan Rating Graph Example
Note : This graph would be embedded in every clan home page if this system was adopted, much like the player profile page.
So, the variables in the rating calculations are
- Each clans rating at the time of the challenge.
- The size of the challenge (preference for more players)
- The number of games won. (If you lose a large challenge by a single game, the rating damage will be limited)
A rating system such as this could remove the current annual system, and just be an on-going rating. (Much the same as any player rating currently)
This will shake up the existing tables, of course, but any clans who have consistently won challenges against other well rated clans will remain well placed.
Feel free to rip into this below! Have fun (but PLEASE keep on topic).
(edit:I wont be able to post to this thread until tomorrow AM GMT, sorry!)