Why is that a problem? Sharing IP for teamates? not a problem. Also you would have to win the game and get majority 3 votes to be MVP if they voter for eachother in a 4man premade that would give 1 of them 2 votes not enough for MVP and no extra IP doled out.
So 1st game player 1 votes player 2(cant vote for your self id imagine) then players 2,3,4 vote player 1 player one gets it.
2nd game players 1,3,4 vote 2, 2 votes 1
and so on with them simply sharing it out to give it to their friends and them selves so unless you are playing with incredibly moral people that do it how it should be and not so that they get it as much as possible it would be rare that even if a player carries a team 500/0/100 that they would get it.