How did VMware Fusion 4 do it though? They just distributed the whole VM as a single .app, with all kexts loads/unload dynamically on launch.
Out of curiosity: is there a downside to pkg's?
http://michaelobrien.info/blog/2009/07/authorizationexecutew...
About PKGs: I think that they're okay, but, historically, they're maligned for being "black boxes" that install files all over your system. App files, OTOH, are (99% of the time) clean, live on /Applications, and sometimes use ~/Library.
It's assumed that an .app, however, will remain self-contained.
https://developer.apple.com/library/mac/#documentation/Secur...