Chandler
This is what I stated above. The notation program doesn't have to write data directly to Sonar, it only has to send midi data and have Sonar play it, just like any other midi controller. It would work in the same way as rewire, but of course it would be easier to use and have extra features. The reason I choose the editors above is because you can edit things like midi CC data within the program, so you wouldn't have to write anything to Sonar. If it were integrated in Sonar, you'd be able to do things like fast bounces and automatic midi track creation, which would save a lot of time and avoid potential pitfalls that could come along with just passing midi. All notation programs play midi and Sonar can receive midi, so it shouldn't be that hard to route the midi stream into a Sonar midi track. Just that by itself solves 90% of the problems people have with notation in Sonar. Of course I'd like a great native Sonar notation editor, but at this point we can't even get fixes. This seems like the fastest and easiest way to solve people's problems.
The path every notation program went is that way - doubling what's in a daw already.
Talked to people at Finale 12 years ago - to do what you ask for - integrate into existing daw software. But no, they doubled up making audio integrated into their software instead.
The natural extension is pretty much doing what Sonar staff view do now - but provide every bit that full fledged notation software do.
To move midi editing, even a tiny step, away from daw - no thanks.
That would make less a recording tool.
But best if both daw and notation can run as rewire host and rewire client - then everybody can work as they prefer. From staff or from recording tape machine as base. For me the notation is the very last step - getting what's recorded on paper to register a song, provide staff and melody+lyrics for vocalist preparing to record, staff for hired people doing horns or whatever.
ARA - audio randow access - is something that Celemony developed for exchanging audio back and forth between a plugin and daw. Now in Sonar, but developed for melodyne needs really. So the same thing for midi - what a treat that would be, for notation and other stuff too. Notation want the midi and takes it - and puts back. So a new MRA - midi random access - standard developed by Cakewalk maybe. So many midi purposes would be extended by this.