OK, so the Stalker girl shorts and LD Tank Top was more of a cheat.  (sorry, that was me too)  I just positioned it close, dropped a smoothing modifier on it, and wham-o, nice fit! 

(...did I mention how much I love that smoothing modifier?)

For an extreme pose, that would not work...so, I looked into how to "create a clone", figuring if I had one, I could autofit.

Found this LINK in the forumarchive, and I got to work. 

As a result, it is possible to get a "decent" autofit of V4 clothes on Dawn in DS via autofit.  I loaded V4 and Dawn, and dialed in the closest possible match of V4 that I could, with Dawn's available settings.  Once done, I save this as a single morph, changed it to a Clone type and saved it off as a Clone morph asset.  (this is a one-time operation, easy to doco)
 
Now I load clothes for V4, and there is an autofit option for this clone from V4toDawn (that's what I named it).  This gets me about 75-80% of the way there...and the smoothing modifier finishes the job.  Morphs are still in the clothes (which I didn't expect), as an added benefit!
 
Just another reason that having a figure native to the application is a real benefit!

I did this quickly, and my feeling is that if someone takes their time to create a V4 morph for Dawn, it would vastly improve the autofit's first pass.  ("V4, A3, etc. Shapes" for Dawn would probably sell very well...hint, hint, content developers...but don't make it too expensive!)