IMO, he would look better with a moderate razor job. I'd at least get rid of the white hairs around the muzzle, then blend to the line of the halter with a #50 blade.
It does take practice, but it does grow back quickly. At least in my observation it does.
Within a week, you can barely tell they were anything but clipped as the whiskers are so short.
Practice and also don't forget to make up for the lack of hair on their nose, and keep them out of the direct sun and very cold weather until it grows back to a good length.
I have been razoring since 1999, and it IS something you need to practice, but look at lots of photos and you will learn what and how. Your horse will be different, too, and you will find that certain things make him look better or worse, and adjust your clip accordingly.
Razoring does not hurt them and I like the way it looks. It is far easier to prep a razored horse for the ring as you only add baby oil and go. I don't do the high-gloss patent skin look, though. I only do a light sheen look on the skin as in rub the baby oil in. I really detest the high-gloss dripping look. Ugh. I believe many judges do, too. I've overheard more than one complaining about the black makeup combined with the baby oil. Ew.
As far as the rule about razoring, I have not heard that it was anything but legal. That said, I don't see much reason to razor anywhere else other than the muzzle (unless it was a surgical or medical issue, but that's a whole 'nother ball of wax).
I do, however, on a select few horses, razor over the eyes a small strip, and then blend with the #50. Most times, though, my preference is to merely clip with the #50 blade. Depends on the horse, though.
Liz