I don't know about this one.
Life goes on. If (at some time in history) the only soprano who could
sing a role was a fat one, then by all means we should engage her for
the job. But this is the 21st century; presumably there are dozens of
sopranos who can sing, act, *and* fit the costumes.
In all fairness, I think the male singers should be held to the same
standards.
On the other hand, I think work must certainly be found for
costume-challenged former opera stars. It is a quandary. What can they
do, other than sing?
Arch