The suggested change to generalize support for libedit to other platforms is a new feature so, by default, it would first appear in a new feature release, e.g. 3.6.  There would probably have to be an exception granted to add it to 2.7.x or other 3.x releases, which are in maintenance mode.  I think the quickest workarounds are to either link Python with GNU readline or, if that is not acceptable, persuade FreeBSD to carry a patch similar to the one you suggested for their current versions of Python.  WRT Linux, it looks like Debian has both a libeditline0 package (presumably the old ABI) and a libedit2 package and their lldb package is linked with the latter.  (The Debian Pythons are always linked with GNU readline.)