A trigger can resolve this...
Player Group - Pick every player in (All players matching (((Matching player) controller) Equal to User)) and do (Actions)
Now, if you want to give new units to every player in this group, you can, or you can give them randomly to any one member. This function in a trigger will differentiate user players from non-user ones. At least, it should. If this doesn't work, then try this instead...
Player Group - Pick every player in (All players matching (((Matching player) slot status) Equal to Is playing)) and do (Actions)