Custom unaccent rules in heroku
I contacted Heroku after trying to find a solution for the exact same issue. Here is the response:


  Unfortunately, there is no way to upload that unaccent.rules file to
  the Postgres server that hosts your database. You can enable the
  unaccent extension, but not supply a custom rules files. If this is a
  requirement for your app to run, you will unfortunately have to find a
  workaround that doesn't rely on the unaccent.rules file.


So the shadow column might be the way to go for heroku after all.