It's definitely possible, and actually pretty simple. This would obviously deserve its own plugin though. I actually made something like this for PHP files but I can't seem to find it. It's posted somewhere on the forum...
Unfortunately, I don't have the time to take on another project, I'm already working on too many. I'm sure someone else will step up though to make it.
This is intentional. AutoFileName has more uses other than just HTML. It's meant to be as versatile as possible. Though it triggers inside ALL strings, you can simply ignore it and it should not get in the way of your normal completions.
Thanks. I'm glad you like it.