Love how you have included bulkheads - they make everything seem so much more streamlined and finished.

our cavity sliders don't have a track on the floor although the wall needs to be reinforced if you want to mount a towel rail on a wall with a cavity slider inside.. in 35 years we had to replace the fittings on one door (out of five cavity sliders) but you need to make sure that the fittings are good quality but the door will probably be open most of the time and a simple floor mounted door stop installed close to the wall will stop the door hitting anything without being a trip hazzard

why not install a lower concrete base this time to avoid future problems or add sand and a new timber edge and a landscaper could do this job for you and they will have to move the shed to prepare the new foundation so make sure that you're happy with the locations and direction of the doors and width of the pad as this is an opportunity to make any changes

However, the rubber square stoppers..... they can look like a wart on a wall. When the door covers them great, but for instance, I have one at my front door, when the door is closed, it is very noticeable. A floor mounted stopper for a door that is mostly closed, in my opinion would be better. And the floor mounted stopper would not be a tripping hazard, unless someone is walking along the wall. Use the square rubber wall stoppers for private rooms.