I've managed to port an old Redhat patch which enabled the use of a gtk2 widget instead of the default motif widget for the locked screen login dialog. Tested on amd64 and works fine, enabled via useflag.
Created attachment 94661 [details, diff] xscreensaver-5.00-gtk2-lock.patch
Created attachment 94662 [details] xscreensaver-5.00.ebuild (modified)
Sorry, but no - we won't include this patch: we try to stick with what upstream provides and patch only what is necessary. You can send this patch upstream.