Legislatures have been in the business of limiting judicial discretion for centuries. It is nothing new. However, you are talking about changing the law by subtraction, not addition, so it only increases judicial discretion. By telling the court they are not allowed to consider the child, you haven't told them what they should consider instead. That means they can do just about anything. If they didn't have BIC, they would still do whatever they want.
It will never happen, but even if it did, nothing would change.