it is normal to call 'Cancel IFR' when going around from the final missed approach into the visual circuit
I agree that is possible, but I would dispute it is normal - I have never done it. Why not just fly the visual circuit under IFR (just like we used to have to do at Night in the UK)?
Even a combined MEP/IR-ME flight test could, I would suggest, be completed completely IFR if so wished.
Not possible for a combined SEP/IR-SE flight test due to the Engine Failure test element not allowing maintenance of 1.000' above highest object, etc.