Why do VAR referees have to be actual referees? Opening up the position to those who are way short of those fitness levels and may not have the man-management skills of referees, such as they are, will give a massively larger pool from which to source the very best at making VAR decisions. It's such a different skill that it's unlikely the best at one will also be the best at the other.
Agree, as long as the final decision remains with the on field official to retain their ability to interpret the Law as is required and appropriate.