All these workarounds sound like a reason to use start using tramp more (apropos, https://www.youtube.com/watch?v=dljNabciEGg / http://www.howardism.org/Technical/Emacs/literate-devops.htm... is a pretty neat demo of combining org-babel and tramp).
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There is also emamux, which seems to be able to copy from tmux: https://github.com/syohex/emacs-emamux/#emamuxyank-from-list...