==The turning on and off of epigenetic markers
As I explained to you before, epigenetics is involved in a lot more than simply turning genes on or off. Surely you must know that by now?
In biology, the term epigenetics refers to changes in gene expression. These changes may remain through cell divisions for the remainder of the cell's life. Sometimes the changes last for multiple generations. However, there is NO CHANGE IN THE UNDERLYING DNA SEQUENCE OF THE ORGANIMS (emphesis added),[1] instead, environmental factors cause the organism's genes to behave (or “express themselves”) differently.[2] The best example of epigenetic changes in eukaryotic biology is the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo which in turn become fully differentiated cells. In other words, a single fertilized egg cell - the zygote - changes into the many cell types including neurons, muscle cells, epithelium, blood vessels et cetera as it continues to divide. It does so by a process of activating some genes while silencing others.[3]
http://en.wikipedia.org/wiki/Epigenetics
Epigenetics is not a magic word that makes the random go away. Epigenetic markers are just as subject to mutation and natural selection as any other relevant DNA sequence.
An organism that changes its epigenetics will express genes in a different pattern but will not CHANGE THE ACTUAL GENE EXPRESSED. Therefore when you say epigenetics is the answer for how genetic variability arises you need to propose a mechanism whereby epigenetics actually changes genetic alleles rather than just changing what genes are expressed in what cells.