I like this idea, it forces teams to split up to accomplish different objectives. Small defending team, scouts, and an attack team to kill other marked enemy players.

They could change the minimap feature to not show enemies in combat either, and only display the marked players. This would force teams to at least have a few scouts. Losing a marked player and killin a marked enemy should award the same points though in my opinion. With the exception of slight scaling based on the rank of battle high a marked player has. It would discourage spawn camping the losing team and make attacking winning teams much more obviously rewarding.