Sepp, thanks for bringing us back on topic.
Going back to the above where Awkwright refers to a multi-crew operation, then they would have to be qualified as flight crew and that would depend on whether the aircraft was operated as PT or CAT.
PT would require 2 pilots anyway and CAT would require flight crew qualified in accordance with EU-OPS Subpart N.
Unless anyone can show me otherwise, I cannot see anywhere in the ANO or EU-OPS that allows for an unqualified, non type rated person to operate as flight crew in the safety pilot role described above.