I been dedicated to Sonar for over 13 years and I love the progress so here are a few suggestion that I think would take us over the top.
Plugin Browser
It would be perfect to Drag and Drop plug-ins in the within the browser
MIDI Controller
This may be far fetched but if we could create a customizable MIDI Map plugin to help Sonar communicate better with various MIDI Controllers
Live Plugin Module
Create a live module to host VST plugins to be used in a Live Setting and be seamlessly auditioned and even recorded with no latency or artifacts