Audiosnap question for a remix of non-grid audio:

As said above, I've got stems from a song recorded sans click. I want to get them gridded so I can sequence to it, BUT I also want to do some tempo manipulation as part of the piece. The song itself has a hard tempo change but ultimately I want to turn that into a gradual ramp.
 
So, I'm having problems with my workflow. All of the "Set Measure/Beat At Now" and clip map alteration/set project from clip don't seem like the ticket because they create a tempo map that I ultimately want to nuke anyway. Besides, I can edit the clip map for one clip all I want, there doesn't seem to be an easy way to make other clips follow that?
 
But, what I really want to do is just quantize ALL the audio to the grid and then make my tempo change happen later. Problem is SONAR is not guessing the tempos even remotely correctly. So, what do I do first?