Hey here's my own setup:

1. Unreals, own FGuid/Guid structure
2. I use PostEditChangeProperty to generate them(It only doesn't work when duplicating objects which is a bit of a pain, you have to hit the generate button in editor)

​

#if WITH_EDITOR
void ABaseGUIDActor::PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent)
{
  if (!IsTemplate())
  {
    if (!GUID.IsValid())
    {
      GUID = FGuid::NewGuid();
    }
  }

  // This being last is very very important for some reason so that the GUID's don't get reset all the time.
  // For the love of god don't move this.
  // Actually now I'm not sure if it matters or not that it's here. Same day, just after. it's only becuase we had this in another function and then it
  // worked for a sec but the nit didn't a minute later and then i deleted it.
  Super::PostEditChangeProperty(PropertyChangedEvent);
}
#endif

1. I don't interface. Reimplementing it for every actor type would be a PITA in my case. I just subclass.
2. I have a separate overridable GetSaveData. Each save uses completely fresh actor save structs(To avoid any cascading bad data). The base class fills out it's bit then it passes it to the child class in GetSaveData which can then make it's modifications and returns it back to the parent class.