It can be the perfect if the exercises are adapted, and all high impact exercises are removed.
The high impact exercises can be hard in the body, but all high repetition exercises that ballerinas do can be excellent in the hands of a skilled trainer.
I think that all exercises can be good until it is proved wrong.
So, I use a few ballet exercises when specific targets are required.
For more tips, download my books or exercise videos available on this website.
Is the old ballet still a current fitness trend?