Perhaps there could be two versions of a hardcore mode- one where you and your friends only have one life per person total, and one where each teen has one life, so in singleplayer you get four lives with each of the four teens, in two player, you can have two "lives" each, or a 1/3 split, with three players only one of the players gets a second life, and four players would play out like the first version unless someone leaves the game instead of dying, which allows the unplayed teen as an extra life, same way with the other versions.