Most sliding door systems are supplied with cages to form the pocket. These are perfect for keeping wall thicknesses reduced. These cages can be very flexible if only covered with one single skim of plasterboard. Someone or something leaning against it for a long period of time could bend the cage into the door, furthermore potentially causing permanent damage to it.
As a bare minimum requirement I would recommend to clad these systems in a WBP ply before plaster boarding to make the wall a lot more stable and less likely to bend or flex. This is fine for standard plastered walls but wouldn't be sufficient for any tiled surfaces on the face of these systems. Even with ply they can still flex slightly which would easily crack any grouted joints. Optimally I would suggest the cage needs to be cladded with 2” x 2” studs to really stabilise the wall on standard height doors. Anything taller will require thicker studs (3”x 2” or 4”x 2”).
Why not just form the pocket with studs you ask? Well that’s a preferred idea by my books and how I would always suggest a pocket to be formed, however if the system is fire rated, to achieve the fire rated certification you must fit the complete system the test was carried out on. Meaning the cage also needs to be included. Expense can also be a factor here if there’s a lot of timber required. The only issue with stud walls forming a pocket is that it can make wall thickness’s increase to 220mm+ (depending on stud size) when most standard single brick/stud walls finish at around 130mm.
It’s times like this you need to decide what is more important, a more stable system or more m2 in your rooms? This can be highly dependent on door location as a 2 metre stretch of wall can easily be made thicker without taking too much extra space, however a 5 metre stretch might make it a harder decision to make.