As per one of your previous presentations an E-Stop and Acknowledge button must be added, is this unavoidably necessary or would the system work properly without them too?

At least one emergency stop is a required according to EN ISO 10218-1:2011: Robots and robotic devices – Safety requirements for industrial robots – Part 1: Robots.

An acknowledge button is typically required as well. The robot must not go on working by itself after collisions. The operator must eliminate the collision and ensure that there is no more hazard threatens. Then the operator must deliberately resume operation.