Permeability and Permittivity of free space…

I’ve known for a very long time that the permeability (µ0) and permittivity (ε0) of free space determine the speed of light in a vacuum. I had not realized that this would interact with E=mc2 to alter the mass/energy relationship and thus the balance between matter and energy in the universe. This would seem to have some strange implications (aside from all of the other bad things that happen if the fine structure constant is not a constant) for changes to the way the universe works if either of these constants changes over time (or perhaps even in very high energy environments as were present in the early universe).