It would be nice to include an API to access OS functionality, similar to AWT's Desktop class (HostServices in JavaFX?). Its common use case for desktop apps is to open default application for a particular file, open the default mail client (if set). I like how AWT's Desktop class allows to check if a particular action is supported, this is a plus. What are your opinions?
I think that is a great idea, to be able to respond to in-app URL's.
For example, the ability to register say "myapp://" with the OS and then
have it be able to deep link. Not dissimilar to how iTunes or Torrent
clients bridge that gap between the web and the desktop. Historically
the installer would do this, but to be able to have this native would
allow for deep integration.