I like the idea, but if it's implemented to client side it would provide a benefit to players using modded clients that show all players. To do it the right way it should be implemented to server side, so that the information about player B is sent to player A's client only when A is able to see player B. This would probably be too huge project for current devs.
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I don't want to be the oneThe battles always choose
'Cause inside I realize
That I'm the one confused