Well for instance if your in a "smaller " tank like the M8 and you have eyes on a target like a tiger you cant really hope to do much from more them fifty feet. So you inform your fellow tankers " im marking a tiger _____ distance from you".
The flag is just a small red flag that sticks out above the treeline. ( if the tank is moving the flag doesnt move though)
you really want something like this, only bigger when people are asking for more realistic things?
it would still have to be very large and neon like an icon...and if it doesn't move with the vehicle, what good would it do? i'm playing devil's advocate here...
...if you're with other tankers, it comes down to understanding the tools you have at your disposal, vox, map and tank commanders view with magnified view...say you do spot an enemy vehicle hidden and you want to direct others in your area to it...a quick look around to check relative positions of the friendlies to the enemy vehicle and direction the friendly vehicles are facing compared to you and call it out to each friendly you want to involve using relative positions and ranges.