One of the things i liked most in the multiplayer Game of Thrones LCG were the titles.
Every round the players had to choose a title like "Hand of the King", "Master of Coins" and etc. Each of these titles had an cool ability, like buying more cards and getting more gold, but most important, they had the "Rivals" and "Supports" system.
The Rivals and Supports make each round really dinamic, forbiding attacks against some players and giving rewards when attacking others.
I think that Titles would really fit L5R multiplayer. In L5R lore the clans compete for the various imperial titles (Imperial Advisor, Emerald Champion, etc). And mechanically the Titles prevent that a single player get predate too much by the other players, what, in the end, harms the fun for everyone.