We are trying to do a similar thing too. We have various subscriptions post VM creation to configure the VM to our standard, like added certifications, registering to satellite or install packages for Windows OS. We want to setup a custom property such that when debug is true, any failure from those subscription will stop provisioning but will not trigger disposal process. Modifying subscriptions or generic configuration in VRA 8 all the time is no go, we want to only debug a single VM, whilst allowing other VMs to continue provisioning failure or not. What would be the best practice to get this effect?