Packaging gets not much easier in 8.5 – at least, when hardly stopped by my first problem.
I just tried to port a headless Seaside application (which always uses the application GreaseCoreApp). The application GreaseCoreApp is delivered with the ConfigurationMap PlatformPortability.
PlatformPortability also contains GreaseVASTCoreApp.
GreaseVASTCoreApp has the prerequisites EmClassDevelopment – and at least here it seems to get pretty worse, when doing headless development ….. and you are forced to import development stuff …
This has been changed from 8.03 to 8.5 – and yes, the fix is, that you create your own maps loading system stuff in a different way.