Once a resource is set DISABLED it will ignore further changes to availability until the resource is again enabled. I don't think there is a way to set a resource enabled via REST at this time.
Basically, I don't think you should try and set a resource DISABLED via availability. DISABLED is a special availability that reflects the state of a disabled resource. It should be done via enable/disable resource support and i don't think that is supported by REST at this time. You may want to create a bugzilla asking for that feature. Or, submissions are always welcome if you feel up to the task.