As per PM - an alternative, and (I believe) very workable campaign system. It doesn't have the bells and whistles of the above suggestions, but I think this could actually work...
Simplex campaign rules for Warband:
The aim of this set of rules is to provide meaning and context to clan matchups, or similar non-clan organised play, with the minimum amount of overhead, book-keeping and similar difficulties. No real games master is required, simply someone to accept PM's and update a forum thread weekly.
Essentially, the ideal ruleset should provide a simple way of arranging Clan vs Clan matches, that also gives them a little more to play for.
Clan matches are arranged as and when the clans agree. Any clan can challenge any clan. There is no requirement to accept, and no time limit on when you can play, as we're all friends and adults here.
Clan matches are played with equal numbers of players (agreed between the clans) on a territory they mutally agree.
Clan matches are
Battles, played first-to-seven, with a point clear (i.e. 7-5 or better). This means that clan matches will last up to an hour at most (6-6 with five minute rounds is 12 x 5 = 60 minutes)
A win nets you three points of Renown
A (6-6) draw nets both teams one point of Renown.
A loss gives you nothing.
When the results are reported on a forum thread such as this, the league is updated weekly, and the clans will move up and down the rankings accordingly. If you don't submit your results by that week, there is no problem, but if two clans are vying for victory, tardiness could mean you lose your place.
These rankings are put into tiers of three, which produces a handicap system:
Example, with Renown:
Clan A - 17
Clan B - 15
Clan C - 14
Clan D - 13
Clan E - 12
Clan F - 9
Clan G - 6
Clan H - 4
Clan I - 1
Clan J - 0
The clans are split into tiers of three from the top - each group distant gives the lesser clan +1 round in the bank for the matchup.
This will mean that, for example, if Clan B plays Clan I (a matchup which Clan B should win easily), then Clan I starts with a score of 2-0.
Any new clans join at the bottom with a score of zero.
Mercenaries and alliances are very possible. The total number of players would remain equal, but the main clan would earn three points for victory, and allies would earn a single point for helping out. Handicaps would be derived from the main clan, minus one (to a minimum of zero, the penalty is to reduce the possibility of enticing "ringers" to help you out, but still give you a reason for ganging up.
The purpose of a handicap system is to encourage challenging of the topmost clans, since otherwise the best may find themselves without matches to play.
The map:
There is a map, although it is abstracted. Each of the scores is turned into a percentage, and that percentage of the map is filled in with the clan's colour.
This means that, for example, the top most clan may have a Renown of 70, and the second could have a Renown of 20 - the topmost clan would have the largest section of the map.
The aim would be to control over 50% (? This could be raised or lowered) of the map, and thus establish your dominion over Calradia.
Anything the two competing clans agree about a matchup (different match types, alternative match rules) would be fine, as long as this will result in a clear win/loss/draw situation.
There are many possible things to bolt onto this framework - including inter clan tournaments, champion duels (which could be 1 vs 1 Battles for a round, on agreement) and so forth, but this should provide a workable, minimum fuss system, that doesn't try to do too much, and should give us some meaningful and interesting clan matches so that we can all enjoy this amazing game.