After trying several workarounds unsuccessfully, I've created a patch for nano to support some escape sequences used by iTerm, a terminal program on the Mac that is very popular among programmers.
I'm happy to go into more detail why I think this patch should be accepted and I would be happy to revise the implementation.
The escape sequences I added support for are:
^[^[[a - Option-<up-arrow> - home
^[^[[b - Option-<down-arrow> - end
^[^[[c - Option-<right-arrow> - word_right
^[^[[d - Option-<left-arrow> - word_left
nano then matches the use of these keystrokes by the command line editor.
Please let me know if you are open to accepting a patch for this and/or what adjustments you would like.