I liked your thread, much because I have had the same idea: the yeast ought to live in a bad microcosm at the bottom of the tank.
Regarding why and how yeast is kept in suspension, AW provided two articles that deal with that in the previous thread. The second article, especially, builds a full mathematical model of that problem. It seems as if yeast cells move around both because of convection caused by the overall fermentation and from floating with their own, proper bubbles, but that the adhesion to self produced bubbles differs between species. So yes, it sounds as if some dead yeast could be in suspension, and mostly so when the fermentation is strong. Here is the paper again: