Lens size and weight changes due to many aspects - number of extra corrective/aspherical/low dispersion elements, the _equivalent_ aperture, the number of focus

Lens size and weight changes due to many aspects - number of extra corrective/aspherical/low dispersion elements, the _equivalent_ aperture, the number of focusing motors, whether the lens has optical image stabilization, whether it is weather sealed, whether it is made out of plastic or metal, etc, etc. Its not easy to just isolate for sensor size. But _in general_, you can make small full-frame lenses which will be equivalent to micro four thirds lenses. The problem is that they won't sell. Today, few people want f/2.8, f/4, f/5.6 primes for full-frame. Most people shooting full-frame want F/1.2, F/1.8 or F/1.4 primes.