I've worried about that on my BX24- it has NO protection around the stems.
I noticed some of the big machinery has about a 2" pipe nipple with a pipe cap screwed on covering the entire valve stem- now THAT is protection
I wonder why nobody makes an emergency valve stem that can inserted from the outside until a proper repair can be made? Seems like it would be relatively easy to make with an expanding rubber portion. Probably afraid of liability when some doofus uses it on his SUV, drives 90 and it lets loose
BTW one doesn't have demount/remount the tire to replace a valve stem- I've used a jack under my truck trailer hitch to break the bead and shove the sidewall down far enough to reach inside and insert a new valve stem
