But the airspace & procedure seems to not tolerate mistakes. There ought to be some safety margin. While not the primary fault, it could be improved.
Surprised you say that; to me the airspace design and procedures are absolutely the primary fault. TCAS was literally invented because intersections with crossing traffic occur at cruise level even though airway separation / quadrantal rule should keep you out of each other's way.
This airspace literally has an intersection with crossing traffic designed into it. You can't hit something you're not close to.