ORIGINAL: Sugar
The victory conditions are already versatile. There are decisive victories, majors, minors and draws. Give 3 points to the first, then 2, 1 and 0.
Expanding on this would be a system that calculates each players performance and gives a rank (pvt => 4 star general). Then each players rank (statistics available in SC forum) is visible to opponents in PBEM. Maybe quits are -1 but you are allowed 1 or so a month.
Thinking about it the point system might need more variance like 10 decisive, 8 major, 3 minor, 0 draw, quits -3. Higher ranked players would get less beating lower ranked players and viceversa.
Also if a game in stagnant for 1 month (?) stagnant player gets -8. After 1 month changes to 2 weeks. Notifications of extenuating circumstances possible. Maybe there could be a rank below pvt (potato peeler) for habitual offenders.
Ranking players would add a whole new dimension to the game and increase interest.
This would work well in conjunction with games being compensated for skill level (equilibrium thread).
Of course we would always have to deal with the person who changes ID and says they are new but we deal with that now.