TL;DRBe the designer of your own, very specific buildings.
What ?This is a bigger request and would require a lot of programming, but buildings with varying size would be interesting. For instance: furnaces. We currently have 2X2 or 3X3 models, but what about more? I’m not talking 4X4 or 5X5 specifically, but rather a system where players build corners and fill in the rest like 2X7 or 4X10 etc. The idea is that the larger the area (the more internal space can be dedicated to furnacing) the more efficient it would be by way of “large batch” furnacing. Right now, most materials are put into the furnace to be processed one at a time. With a larger furnace, the idea would be to smelt larger numbers at once.
When the player has access to a steel furnace, crafting could pop up a schematics screen and the player could be tasked with creating the building to their specs, using 1x1 square components like: exhaust/smoke stack (certain number are required per square), storage (the maximum number of units to be smelted at once), and heating element (speed at which one unit is heated). The idea is to make the smelting process take a lot longer, but balance that against being able to batch smelt. Simply design the building and the schematic generates a resource cost.
This could apply to multiple buildings. Steam engines, boilers, and solar panels (with built-in power as seen below) are obvious choices on pure scalability or quality of life. Even belts could be widened to a 2X1 or 3X1. The ultimate limitation is whether buildings in their current implementation (notably their animations) could be broken up and spliced back together in a way that makes visual sense.
Sure, this exists as a mod already in instances of specific buildings, but the appeal is the capacity to create a specific building to your own situational needs. What's more, there's one particular application that I think would serve as the centerpiece: the Algorithmic Assembly Machine, which is an assembly machine that can follow a multi-stage design plan, where square footage directly correlates to how many stages. Essentially, the current research determines how many components can be used in a recipe (in assembly buildings 1, 2 and 3), while a new branch of the research tree would determine how many stages could be stacked. Sure we can already do this with a tangle of conveyors, power lines, and such, but that is so inelegant for end game; imagine being able to allocate research to be able to build a huge building that takes raw resources in and pumps engines, high-level research, or other complex recipes out. Building components would include: assembler (2X2?), storage(1X1), Input/Output (like where fluids can come in/go out), processing (determines number of stages and requires more resources), and others.
Why ?That added little bit of customization that allows for peak efficiency.
How ?A new schematics menu.
Some math for figuring out efficiencies (probably something based on adjacency bonuses in building components)
Tweaking of animations so that they can be modular
Calculation of resources/dependencies for a new branch of a research tree
Hover over flowchart for what is being built
Building stats (does it have one big health bar or does each little piece have one)
Let me know what you think