You see dresses with long skirts as hybrids quite often.  The skirt portion is all made part of the hip group.  The dress is a conforming figure, except there are no leg/feet groups.  This allows you to sleek the hip group and convert it to dynamic cloth and use the simulator to drape the skirt.  If the group seams are weld so that body part groups are all one solid mesh (not sliced) than you do not need to constrain the top (waist) of the hip group.  If however the outfit was made by actually slicing the mesh so that each body part group is separate than you may need to constrain the top (waist) part of the skirt to keep the simulator from causing it to drift free from the abdomen section. 

You would do your pants the same way, make them all hip group.  Or else make the belt abdomen and put the dynamic parts in the hip group.  The mesh should be solid with the body part seams weld together so that the hip part does not come loose from the abdomen part.   If you use only all hip group you probably will have to constrain the top of the pants to keep them in place.

I have experimented with hybrid clothing.  It works okay, and is good for speeding up the posing and draping process since you only need to run the CR on the dynamic parts.  However, IMO, there is not that much to be gain in hybrid over full dynamic, except for maybe things like long full skirts where you can include morphs and body handles to help pose the skirt part - or else run the skirt part as dynamic cloth.   I suppose certain types of sleeves might also benefit.

-Rob