@larry,
in obscure series, that coop characters with special abilities are used a little.

in this game, you generally use 2 characters thought the game, if you play coop each player controls one, if you play alone, one character is AI controlled and one caracter is under control of the player, player can switch active character by pressing a button.

in some parts of the game you need ceratin characters to be together.

i.e. in a puzzle there is a ventilation cover(if that's what it called) on a wall, but it is too high to reach, there is no ladder or something, you have a screwdriver and it's certain you should be going thru the ventilation duct.

To reach the cover, you need to be playing with the most muscular guy with lightest girl. Girl steps on the guys hand, guy raises her up, she uses screwdriver on the cover, then goes in. from that point girl keeps going alone. I dont remember how it continued but probably, we re sending her some items thru the duct, and by controlling her, we were trying to find some way for others to get to the other side.(probably unlocking a locked door or finding a key.)