Why not use the built-in Myth scoring system?
For many game types, the Myth scoring system does not provide a spectrum of possible outcomes (e.g. in Assassin or Last Man on the Hill you either win or you lose, and in Capture the Flag ties are common). Also, many game types that have such a spectrum (Territories and Captures) can lead to ties that Myth treats as victories/defeats. The MWC99 scoring system was devised to remedy these problems and to make all game types worth roughly the same amount in competition.