Mob Cap In MP is shared with all players

Currently the mobcap on MP is global for all players, so that when one player kills mobs/ lights up the area around him, he shifts the mobs to others. this makes it impossible to build efficient mobtraps on 99% of the servers, since all people would have to collaborate to make this working.

So my idea is: how about making a separate mob cap for the 128m sphere around every player, just the same number, but so the mob checks when it spawns if there's any player in 128m range which has more than 79 ( current cap) mobs around him in his 128m range. so in SP this wouldn't change anything, also it wouldn't raise the cap, but it would allow that everyone can build his own separate mobtrap in his area.
Of course it could also work by chunks, but the idea pretty much stays the same.
this would simply make stuff like good mobfarms possible in MP, which i already possible in SP, so its not OP.
Also many people complain about few mobs when they go mobhunting for the same reason.