I think it would be a good idea to have a selection of girls to play the role,like for the Olivers.
Some of the less experienced girlswill probably have vocal problems performing 8 shows a week especially the young ones like Niamh and Jessie.
It would also overcome the problems of the public being disappointed when the understudy has to go on.

Because it would be a nightmare in the booking office! In addition, the critics would be bound to have a preference and that would encourage a class system for the seats, 2/3rds of shows being considered second rate.

With children it's accepatable because of the working rights and need to mix education into their day too.