I'd love to see CWS implement a chord track feature such as the one in Cubase. I think coupled with the arpeggio, it would be inspiring.
Also, I'd like to see CWS implement a mastering suite along the lines with the one in Studio One. I have found it to be extremely convenient when making minute changes to masters.
I master to the K-Metering System. I know there are third-party options but it would be nice if this was available in Sonar as well.
If CW could do this, I could stop shuffling between DAWs every time I want to use an exclusive feature. It would save me money as well because I wouldn't have to update or purchase any other items other than CW. I love the workflow and UI of CW and still use it as my daily driver, but it would allow me to be so much more productive.