On your performance section you mention the different type of blocks have various performance hits to servers. I'm sure you have something like this in place, but a simple "point" heuristic for different types of parts (dynamic/static/size/script resources would change the point value of a single unit piece) could be used to cap the total complexity that a single player can create against on larger servers. The "point" buy is easy to list, e.g. "My cool server (12K)" and allows server owners to keep spam from destroying playability. I suspect you have something like this out there, but I figured I'd hand in my 2 cents.