This method does not stretch audio clips. It's like manual splitting but with some first stage automation.
 
Melodyne detect tempo changes pretty well. Now SONAR can apply tempo map from Melodyne clip region FX.
What if...
 
1) I make Melodyne region fx of (hard gated) drum guide track (maybe kick & snare) and apply tempo map from Melodyne to the project. Now drums are in the grid.
 
2) Move all drum tracks 20 milliseconds to right.
 
3) Split all drum tracks at each measure.
 
4) Move all drum tracks 20 milliseconds to left, back to the original position. Movement was done because now splits are located before transients.
 
5) Remove tempo map and use the original tempo of the project.
 
6) Drums get quantized but there may be empty gaps between slices.
 
7) Edit clip crossfades manually.
 
 
Is this a dead end or a method to develop? I didn't try it yet...
Is it possible to get rid of gaps automatically?
 
 

The problem would be mainly in the overheads. Ringing cymbals are impossible to cut this way.

I do the similar editing manually all the time, including overheads, drum room and other ambience mics. It's quite easy to make edits inaudible if you cut clips at area which doesn't contain transients. Key is to use right kind of crossfading and check results by listening.
 

The Idea I have been trying to figure out is how to change the drums +- a half step to move them onto the current scale of a song, say using Karma as the key source and Melodyne as the destination. Then if the snare and kick pitches are not on the current scale, they get bumped up or down until they are on scale. Two scenarios on this. Midi drums real time and Real drums audio in post production.
 

panup
I do the similar editing manually all the time, including overheads, drum room and other ambience mics. It's quite easy to make edits inaudible if you cut clips at area which doesn't contain transients. Key is to use right kind of crossfading and check results by listening.
 

Me too! Drums are typically the "easiest" (albeit laborious) to fix this way. It would be nice if these steps could be automated