This would be very easy to implement using SJ's
Tech Gridder . Add a tech area such as Miniaturization, or maybe just use Industry. Set it to have, say, 20 levels. Copy whichever components you want to be miniaturizable into a temporary file. Run the tech gridder and add the Miniaturization tech area as a tech grid, making it reduce size and cost by 10% or whatever you would like. Then, paste the generated components over the orginials in Components.txt. Now, whenever you research a level of Miniaturization, the size and/or cost of a whole range of components will decrease by 10%.