The guy in my parish’s RCIA who was named Kyle (and really wanted to use that as his Christian/confirmation name, since he was named after somebody who took a bullet for his dad) is going to be allowed to use that. So you see that I don’t always do this stuff out of sheer language nerdiness….
To be honest, I think that as important as it is to say NO! to stuff that’s wrong, it’s just as important to say YES! to stuff that’s permitted and not totally stupid. (It would be stupid to take the name “Lucifer”, even though there are saints named Lucifer since Romans named kids after the morning/evening star. It goes under the “Sheesh, don’t name your kid Adolf” rule. There are equivalent rules for other realms of human endeavor, too.)
Things that are permissible and part of Christian tradition, or things that could become so, are a sort of holy farmland. It’s okay to leave stuff fallow, but it’s also a good idea to get in there and use what we’ve got. If Kyle was the holy name of hardworking though near-forgotten saints, then bring it out and recall those saints to our minds! If you really want to name your kid Ashley, make sure she gets a holy card of the English martyrs, and knows that she has a holy name, too! Give people a nice solid place to stand, with their namesakes in the Communion of Saints always beside them. But don’t surrender to the world any of the territory that’s really ours, especially through sheer forgetfulness.