So if we regard the somatogravic illusion as a potential "threat" how should this be managed?
This is what they teach during a typical IFR course: do not get yourself into unnecessarily drastic manoeuvres in an IFR environment, don't make too steep turns, control your pitch within limits, trust your instruments, etc. In this example a 25 deg pitch up was completely uncalled for and significantly outside what was required. It was enough for them to follow the FD guidance (assuming of course it was correctly configured).