Purely hydraulic would be very hard! The spheres have diaphragms in em to separate the air from the LFM, the compression of the air provides the springing, the LFM provides the damping.It's not you know. That's why it's called 'hydropneumatic' and not 'hydraulic'.
https://www.autoevolution.com/news/citroen-hydropneumatic-suspension-explained-49954.html
But then you know that by now!
(Sorry, replied to wrong person! meant to be @Interceptorxj !)