I'm not sure that considerable experience in the field of dance is necessary for the role.
It seems to me that the judges work as a team - each primarily taking care of a different aspect of the performance, but all four with some common ground.
Craig's main focus seems to be the technical side.
Bruno's is the artistic side.
Len looks at everything, but not in such fine detail as Craig and Bruno.
Alesha seemed to focus on the look and feel of the performance, trying to judge it more as would the average viewer.
It looks to be a big ask to get Chelsee to a position where she could earn respect if she took over the Alesha role (elocution etc) - but if she was indeed capable of delivering a verdict on a performance which was always impartial and demonstrated some knowledge of the technical requirements of the various dances, imagine how she and Bruno might interact