I would venture a guess that the overall ratings would change
very little, if at all. The public is very fickle. Once a "personality"
is gone, they fade from public perception quickly. As long as the
station continues to play the format to which they are accustomed,
they will tune in, no matter who is in the "air chair". (including voice
tracking or unattended). "Personalities" are subjective, at best.
For every listener who likes Personality A, there is one
that does not. Gain one, lose one. It's a wash...One man's
"revolutionary" is another man's "freedom fighter"...