Is it possible to customize Emacs so that rgrep would correctly find occurrences of some pattern in both UTF8 (or even Latin) and UTF16 files?
I guess we should customize grep-find-template, but can't make my way through it.
EDIT 2017-06-16
I do now have an example of working utf-8/16 cat command for the shell. It should then be transformed for the Emacs's grep, if that's possible. Here it is:
cat $1 | ( [[ $(file -i $1) =~ utf-16be ]] && ( iconv -f UTF-16 -t UTF-8 || true ) || cat )