Have you considered the option to insert the MVP of the game? Imagine,
through some algorithms, the game automatically calculate who deserves MVP status. the algorithm may include (dmg to objectives / champions, minions kills, warding etc.). of course, for supports you may need special calculation.
Ip bonus, does not have to be something special large. If you get the status of "MVP" in the game you get, for example, +50 bonus ip, or something like that .
I think it would inspirisal all people to give their best in every game!
Thanks for your time, I hope that you take into consideration this idea!