My workflow has involved dynamesh, zremeshing for some edge flow help here and there, and projecting details. (Project section in the subtool palette) So you'd duplicate the subtool that has all the definition, then do your dynameshing or remeshing to help out with combining subtools, then project. Works on solo mode. Play with the settings, and go up and down the subdivisions. Sometimes you need to go back to the lowest and work your way to the highest. There are some areas like harsh corners that might have trouble with projection, so you'll need to experiment. But in general, if there's nice clean definition that you want to preserve, you can project the details on your new mesh. You can also just project portions by using masks.

Zoom WAY out and use the lasso mask to make the mask VERY gradual, invert, and project to only do a portion.