I don’t know if what I am about to describe will actually work, but it’s what I would try. Proceed at your own risk, and before starting back up your network qube.
I am assuming the qube you tried renaming is NOT a templateVm but rather an AppVM based on a template VM.
A disposable template is basically the same as a persistent app qube, except that on the second page of settings (advanced), the box for “Disposable Template” has been checked. You have to check that. Then hit “apply” before the next step.
If you want to rename the qube so it ends in dvm (not a bad idea), go back to the basic tab in Settings, and press the “Rename” button. Add -dvm to it. (Note if there are any other unsaved changes they will go away when you do this, which is why I told you to apply the previous change before coming to this step.)
One more step, you probably want your disposable to have the same name always; for that you will want “new qube”, and select disposableVM for type. What should come out of this is a new qube that can serve as sys-net.
BUT BEFORE DOING ANY OF THIS clone your original qube to -BAK just in case none of this works. And you will have to shut down your net qube before doing any of this.
Oh, and I forgot to mention you should back up your present qube before making any changes to it, just in case.