Parents who do not have a habit of reading the law on a regular basis will certainly not know what it means. Changing the language will not change the way people do things. In this case, it will only lead to more arguments between parents who do not understand what it means. The parents will have to consult with one another about most decisions affecting the children. Surely this is unreasonable except in the most extraordinary of situations.
Parents have difficulty co-parenting when they like one another.
This new term will simply provide the abuser with one more means of controlling and harassing his former partner. To require ongoing consultation and joint decision making between an abuser and his victim is profoundly disrespectful of her reality and may well place her in an ongoing dangerous situation. There is nothing wrong with one parent, presumably whoever was the primary caregiver before separation, having primary custody after separation. Children of separating parents will have many changes to adapt to as it is. There may be a move, there will almost surely be a drop in standard of living, there will be feelings of anxiety and insecurity and new relationships with both parents to establish.