Hello!
Also with most airfields around me charging for Instrument approaches it can save the student a fair amount of cash flying the NDB approaches they are most likely to get on test off a local radio station.
I am an instructor, not a student's money saver. If his training plan requires NDB approaches to be flown, then I will happily fly NDB approaches with him. Proper, published, official NDB approaches that he can log in his training records. Real world NDB approaches using real world (aeronautical) NDBs down to real world NDB approach minima, often enough in real instrument meteorological conditions. Only this can show him the real world problems of these approaches. Why ecactly they are called "non precision" approaches. And how far away from the runway they take you and how close to the obstacles. If he wants/needs extra practise at lower cost, then we will do it in the procedures trainer.
But under no circumstances will I ever fly a self-made, unapproved approach procedure and under even "less then no" circumstances will I ever teach someone to fly self-made, unapproved procedures. Flying is expensive. Training to fly is even more expensive. For good reasons!
Greetings, Max