(see Hammy's post on this subject in the thread "First 5.04 game: once again Burgundians vs Byzantines ")
(NB I've edited this post as I've just discovered that BHGS may use this system for FOG at BRITCON)
I discussed scoring systems with Simon Hall at the Leeds competition. Discussion was restricted to points for the actual game result (i.e. not painting, sportsmanship etc). 
The main points were:
1. Some players did not like calculating percentage losses in the BHGS system, so a simple table with a minimum of calculations was desirable.
2. We wanted to avoid the current situation in DBM where a very close game can come down to "If I win this combat, I win 9-1 but if I lose it I lose 9-1". I.e. the final score does not reflect how close the game was.
3. We pretty much took it for granted that it would be "zero-sum" i.e. the two players' score would always add up to a fixed total.
After the discussion I proposed a system somewhat similar (but not identical) to Hammy's suggestion. According to the BHGS web site, it is likely to be used for the Fog of War tournament at BRITCON. 
The underlying principle is that your army is worth a certain number of points and you get a share of those points for the percentage of your own troops surviving and the percentage of the opponent's troops broken . You gain or lose some bonus points if you break the opponent's army or your army is broken. (This is a key difference from Hammy's suggetion where you get a bonus for winning but don't get a penalty for losing)
The main question is how many of the points come from attrition and how many from the win bonus. 
My personal feeling is that the win bonus should be relatively small because in a close run thing the win is mainly determined by luck. BHGS seem to be going with 26 points for attrition and 6 for winning (these numbers are easy to change). Then if you are almost at breaking point when you win, you score 13-19. This is the same score as a draw in which you are 25% of the way to breaking the opponent and lost nothing yourself. If you win by a large margin then this will be reflected through the points you get for attrition.
The system is implemented through a table which avoids the need for calculating your percentage losses. The table gives you a number, which I call the "Attrition Ratio", based on the size of your army and your lost Attrition Points. The win bonus is automatically accounted for in the table, so the only calculation is:
Your score = 16 plus (opponent attrition ratio) minus (own attrition ratio). 
BHGS have put the table on the net at  
http://www.bhgs.co.uk/Nationals/rules/FOGrules.htm
The instructions for using the table to find your Attrition Ratio (in case it's not self-evident) are:
                                                   
1    Locate the number of battle groups in your army at the top of the table.                     
2    Read down the column until you find the largest number less than or equal to your AP lost.   
3    If lost attrition points is equal to or more than the number of BG in the army, then use the "ALL" row.  
4    Go to the right hand end of the row and read the corresponding AR.                                              
The table on the BHGS site has a couple of cells highlighted which correspond to an example in which :
"Red" had an army of 10 BG and lost 3 AP. (AR = 3)
"Blue" had an army of 16 BG and lost 13 AP. (AR = 11)
"Red" score = 16 + 11 - 3 = 24
"Blue" score = 16 + 3 - 11 = 8