Oleg - I was thinking of including something like the cultural facility or cities from proportions but maybe even something like giving reduced construction abilities to planets with low populations. For example a colony of 20 million would only build at 20% instead - combine this with increased population weight and it simulates the proportion mod feeling without the extra work.
Here is a image I just threw together in ten minutes of a galaxy class ship to give an idea of what I meant by original images...keep in mind it has no textures, so it will look much better when it does...
Galaxy Class