I have a conceptual question.
Can anyone see any reason why one couldn't apply subsurf to the default mesh to produce a higher resolution mesh, make the current default a proxy topology of that, and regenerate the targets just by taking the difference between the subsurfed default and the subsurfed morphed mesh?
It seem to me that Blender can deal with meshes of that size without any problem on my machine which is not high-powered by any stretch.
For those of us who are doing still renders it would be nice to be able to work with higher resolution meshes when producing new targets. When I was working on jawlines it was quite frustrating that the mesh topology didn't align with the jawline and I therefore got nasty artifacts. I've got the same issue with sculpting defined pectoral muscles or abdominal muscles using the default mesh. Working with a subdivided mesh those issues would likely largely go away. Just generally one could have more body and target detail.
I haven't tried it yet myself but it seems that a lot of people are sculpting at a higher resolution and then using that to generate normal maps to "fake" higher resolution. If you are doing static images and don't need high performance, wouldn't it be nice to be able to use the sculpted mesh directly?
Anyway, I'm not asking anyone to do this, I'm just wondering if there are issues that I'm missing that would cause problems.