I'm sorry, but I don't know much about Old Norse at all. So I won't interfere with your little discussion. But to my ears Hayley has nothing to it that would remind me of any Norse name or name element I have ever heard of.
You never know what happens to names when they cross a border (of space or time), but like you said, what should the Norse name have been, and what border could have been involved?
I don't know much about trends and changes of meanings, like the ones you are talking about, but what you say sounds reasonable. Even more what you write about name books and especially sites like babynames.com.