Virtually There the problem with your argument is that you can't guarantee terrain separation. If you are below the MSA/Radar LSALT in cloud and either you go out of tolerance or the aid fails how are you going to guarantee terrain separation? Procedures are built around certain tolerances and if you go outside that or can't determine your position how do you know you won't hit a hill somewhere?
You either have to be visual, or if in cloud on an approach or radar LSALT or above a MSA.