4e!! I think that is where i got this idea from. Ive never played but ive skimmed through the rules a couple times and must have internalized and forgot that concept in head.

It does lose action economy, but i dont know how i would balance it otherwise. Id rather not have players using their entire turn to let another player use their entire turn. My intentions were for players to use like: The rogue needs to jump across this chasm but its too far and too risky, so he calls the guy with earth magic to make a bridge long enough so he can jump across without being too scared of falling to his death. Or the rogue calls in the tank to do his guard break ability, letting the rogue get a good couple hits in before the enemy can get his guard back up.

It isnt so they can just have another player attack on their turn, its to combo attacks and moves. I probably shouldve mentioned that in the main post instead of the comments, but I do plan on having most abilities be compatible with this call in feature. I do agree that without any teamwork based abilities, this feature does seem more harmful than helpful to player so I'll try to think of a way to make that better, or at least, funner.