Well, the 100% solution is to "for all sub projects in sbt build" grab "resourceDirectories in Compile" and make sure you change any application.secret that shows up in *any* valid typesafe config file in any of these, using some kind of refactoring/reformatting tool.

This is the "most simple" solution.   I wasn't sure "how far" to go to the full solution, so I stopped at what I consider 99% right now.  Your version of the filter actually looks better, think we should bump to that?  It's not quite the 100% solution, but it's pretty darn close.