You are starting with a mutation, considering the phenotype and any differences and attributing that as evidence of non-random mutation. The phenotype is a result of the genotype and the environment. This is true of any phenotype whether arising from mutation or the wild type. A random change in a gene does not have to result in an alteration of the phenotype. What you are saying is that the 10 people with the mutation are being subjected to different selection pressure which would be true if they were in 10 different environments. Do you see what I am saying? There is no reason to think that 10 people with the same mutation would not express a phenotype that was pretty much the same and subject to the same selective forces or not if it is neutral. Differences could occur based on the dominance of the mutation or in heterzygosity/homozygosity. We see this in sickle cell disease. The heterozygous condition in the presence of the selection pressure conveys resistance to a disease. The homozygous condition or the absence of selection pressure on the heterozygous condition is a disease.<quoted text>
Here is what I am saying. If 10 people have the same said mutation but the changes/variation it causes is different for them, then it is not a random mutation, it is a random effect of the mutation.
What you seem to want is an environmental factor that causes a specific mutation, at a specific point resulting in a specific phenotype. There may be some natural mechanisms that exist that can do this, but I don't know of any and certainly they are not the dominant mechanisms. Science can select a specific gene and move it into a new genome, but there is still a large random component. There are "site directed mutatagensis" methods for instigating artificial mutations at specific points, but these don't occur outside the lab.
The mutations remain the totally random component of the two step process.