Planning applications are minds games between planners and applicants.

If he has previous experience in planning you may end up helping him not hindering him.

The final use/ change is sometimes deliberately NOT declared at first application especially in sensitive applications like Listed.

He may know exactly what he's doing and yours and others objections might be exactly what he is hoping for, to prove to the planners what he is asking for won't be acceptable, but then what he actually wants to do suddenly becomes the only option.

.