It's very frustrating that Emacs lacks support for xwidget just because of the packaging issues with webkit! The same reasoning seems to apply to a broad range of packages which depends on webkit2gtk (say, liferea, evolution).
I suggest that Debian provide a separate repository called 'insecure' for the stable branch, which includes software without security guarantees for the sake of usability. There 'emacs-xwidget' or something like that can be put.