Thing is, Sonar is still having to play each track and mix all the individual tracks in real-time to busses, and then to the Master buss. So, in a large 50+ session, Sonar is still having to do so much work, you can't always (almost never) record with less buffer without drop-outs. But to have the entire mix temporarily frozen (mixed-down) to a single stereo track, or to stems, would open up so much free CPU room for Sonar. That could, in a sense, be the same as Exporting the entire project to a stereo track, opening the stereo track in a whole new project and arm Track #3.
Or, exporting Guitars, bass, Drums, keys as four individual stems to a whole new project, where you can use Tracks 5-10 to record low-latency vocals with very little risk of drop-outs at all. BUT, if you had a Global Freeze, I wouldn't have to do what I nearly always have to, described here. I could keep adding tracks to my session and breach even 100+ tracks with no sweat.
Sheesh, maybe even allow buss-freezing, where-by the function would mix/freeze all the individual tracks to the buss, so that those tracks don't play, but rather a mixdown, controlled by the buss fader alone.
The general idea is to get the massive intense CPU processing out of the way while trying to track additional overdubs. Currently, there is no excellent way to do this, and/or Sonar really isn't built to handle more than 20-30 tracks (my perception).