wget is the command line program to do what you’re saying. Or what I use, anyway. Not tied to a browser, though. Maybe you could export your history and pipe it into wget if you’re using Linux or have a Linux-like command line?

I also use the FF SingleFile plugin. Again, not automatic, though.

Maybe I’m not following, but the fear is that government requirements amount to an ID requirement, which makes anonymous posting impossible. That’s why I care about IDs, at least.