If light is a wave and electrons are the medium, the speed of a light is a consequence of the forces between electrons and the inertia of the electrons. In different types of matter, where electrons are more or less free to move the speed of light is different.
It seems like the forces between the electrons would have to have a higher speed of propagation than light so that after the inertia is overcome the speed of the wave would be the speed of light.
One objection I get is "to get electrons moving at the speed of light would take infinite energy". This comes from the mistaken idea that if the wave is propagating at the speed of light then the particles in the medium have to move at that speed. You can see that this is not so by looking at a tsunami wave in water. The water molecules move slowly yet the wave may be moving at 600 MPH. Also, light is a transverse wave, not a longitudinal wave like sound. So the medium is not moving in the direction the wave is moving. The electrons do not need to move at the speed the wave moves at. An even better example is that electricity propagates down a wire at the speed of light even though the electrons in the wire are not moving very fast.