Instead of having fleet missle do % of extra damage to your target, have it tag your target so you can tell where they are.
At lv 1, you'd get to track 1 target
at lv 2, you'd get to track 2 targets
at lv 3, you'd get to track 3 targets.
Each level will have 1 charge
Each charge will cost 7 cp (maybe more?)
To be able to see where your target is, you would use a command, such as /Track 1, /Track 2, /Track 3. You would be shown the target's coordinates and whether they are alive or dead. It will not show the targets name (just in case they hit the wrong person) If the archer hits the same target more than once, that target will take up more than one space. (i.e. If you suck with the skill, you could have the same person assigned to all 3 trackers)
A hit landing on a monster should have no effect.
Once you have your targets hit, you don't get to change targets until you switch maps. The only way for a targetted person to stop being targetted is to switch maps. If the target switches maps, it will allow for the archer to track a new player in their place.
I think the way Fleet Missle shoots should remain the same since it seems pretty hard to aim and the benefits from landing a shot with this skill would be pretty huge in pk in places like mazes and trying to hide priests in war.
If a player is being tracked, it shouldn't change the color of their character, but there should be a way for players to check if they have been tagged with a tracker with a command like /Tracked which would show a response of yes/no and (maybe) give the name of the player tracking them.