Whilst filenames and titled are linked in the current default template, it shouldn’t prevent you from modifying the title of your files. The only title which matters is the one specified via #+title:, not the filename. We’re looking into ways to update the filename on title-renames, but we’re also considering dropping the slugs entirely.
That being said, for your use-case, I think you’d be better off taking transient notes inside a daily-note, and eventually refine them by creating a new fully-fledged note when you have enough data.