>I would like to start adopting the plugin sources to >- have their encoding parameter default to null, meaning platform encoding > as before
Yep. >- output a warning message if the encoding is unspecified Is a warning really needed? Perhaps just an INFO that says "using platform default encoding: [value]". Again going under the theory that someone that needs to worry about the encoding will be looking for it, shoving a warning in everyone's face that doesn't care isn't a great choice.