Just like shvrdavid - I tried most of your ideas.

Most useful I found dynamic water or mattress surface. (Dynamic Furniture in marketplace)

Water drop looks good if there is no collision. It looks weird if water falls through the body.

Skin over skeleton must be prepared for particular animation and single move. Other way folds apear in wrong areas. I think that it could be solved creating many dynamic groups with different fold resist density etc. I had no patience to continue experiment and now it is useles because WM does the same.

I made dynamic rubber or snot. It worked well but was pretty useles. Nasty animation.

Body morphs is good idea, but they are limited to single body part. Anyway some morphs like breast gravity are easy to create and look good.

Dynamic cloth-hair are great, but hair must be made as soft decorated group.

Here you can see draft. Unvisible dynamic group is a cap pinned to the top of head with single line of verticles, selected as choreographed. Over dynamic group are strands which are soft decorated, except few choreographed verticles on the top. I found few problems. This kind of hair cannot be used in all position, for example upside-down. Anyway the most problem was that I cannot create good transmap and texture ;)