As an examining captain, you would have no choice but to fail someone that slipped a large aircraft...but that's not the point. It's the absolute absence of the skill "up one's sleeve" that worries me.
Based on nothing more than a gut feeling, I would doubt that side-load airflow alone would damage a pylon, bearing in mind that slipping, if done at all, would be at low speed. However, I would readily accept that the lateral accelerations and complex rotational g-forces would have to be kept to an absolute minimum. Johnson's maneuvers come to mind.
I recall a very respected training captain in the early 60s, who would take us over the threshold at 1,500 feet, and tell us to land. It was a simple and fun exercise, and the fact that I can remember it so clearly all these years later, must mean that it was well ingrained.
Another captain used to push us into doing a 60 degree bank turns at 500 at Teeside. I still recall him chuckling as I put on full noise. Great fun and such a good grounding in learning the feel.