I don't think this can be done in a way that is not arbitrary, so I will state my position clearly. I consider this an arbitrary cruel and inhuman punishment, as I consider, for example, the death penalty cruel and inhuman punishment.
You can name a crime, you can give me a scenario, however heinous and horrible it is, and say, well, wouldn't you want to deprive somebody citizenship in those circumstances? I will say, as with the death penalty, however horrible the crime that somebody has committed, the death penalty is a violation of fundamental rights and you can't do it. It is the same here.
There's no fair process, just as there's no fair process for sentencing somebody to death.