For the past few days I've been talking about stages (rocket stages) as gameplay. Today I wanted to talk about stages that continue to operate.
A big problem with Kerbal's "rocket stage design" philosophy is that each stage tends to be kind of fire-and-forget. There is some interaction between the phases, mostly in terms of physical dependencies, but nearly all the effort is simply to get the payload to the destination. Nearly all of the stages are disposable.
But the most interesting things are done when you have stages that are complex. Launch a space station hub which drops a lander that has a skyhook... that's when things get interesting. A lot of stages that have complex, ongoing functions.
So let's forget the harsh physics sim and focus on the idea of having a system where you create stages that continue to do stuff. For example, if you want to mine the moon, you have an orbital base which drops the mining facility which has a heavy lift shuttle to bring the payload back to the base...
The key here is how to make the physicality of the stages matter to each other. If it's all just standardized docking modules and dropping stuff, then we end up with a cargo-box situation where it doesn't matter what the space station is dropping. Just use the same space station regardless of what we're dropping. No! We want it to matter. But how?
Let's make our game a sort of Battlestar Galactica thing, where you're on the run and you can only stop for a few weeks at any given resting point. When you drop a mining facility, you're going to want most of that stuff back before you leave, stowed away securely for the rigors of warp travel. You might leave some scaffolding and concrete behind, sure, but those mining lasers and solar panels are too valuable to ditch. So every stage you launch, you plan to bring the vast majority of it back and reconnect it.
Now the physicality of the design matters, because not only do you have to drop it, you also have to resecure it, and in a way that is safe for warp travel.
I'm picturing something like a giant space donut with a bunch of big "patches" on the outside. Those patches are places you can construct your ships, and the places you'll want to reattach them to. Of course, the ships you create are often very complex, multi-stage objects, since they do have to operate in complex environments at interplanetary ranges. You could launch your fuel station and your mining facility separately, but it probably makes more sense to combine them into a single ship and return the facility to the fuel station rather than trekking them both back to the hub with independent microwarp drives.
Also, you have to choose how much to leave behind. The mining facility has a few very high-value modules - laser drills, for example. Perhaps you just want to reclaim those, so you load them and the crew onto the ore shuttle and leave behind the majority of the facility framework. On the other hand, infrastructure struts aren't free either - maybe you really do want to recover the majority of the facility. Perhaps even to the point of recollapsing inflatable hab units and deconstituting concrete back into powder for reuse. It depends on gravity and time, I suppose. And how much work you feel like doing to set it all back up again at the next respite.
I also like the idea of very adaptive physical objects. The space station unfolds when it reaches orbit. The shuttle has "wings" of plasma to help lift it, but it needs to be careful not to cut the space station. The facility can "self destruct" and pack itself into a box for cargo lifting. Even habitable modules might migrate around a facility shift-by-shift to keep the workers all perfectly rested and happy...
The big thing here is the recovery of each stage. This makes it critical for stages to be able to re-dock with each other, or be dismantled into easily-carried parts. Either way, it's clear that the physics of the game will have to be a lot more forgiving than Kerbal's. In fact, the piloting and docking is probably done automatically, with you simply choosing destinations and directing crew as to what to build or change when something needs building or changing.
This automation will allow you to steadily build up your capabilities such that even on a short respite you could deploy hundreds of mining ships to strip a star system bare in just a few weeks. Of course, the final goal is to fill the donut hole with an intergalactic drive and leave to find a green planet in some other galaxy... but who will manage to gather the rare resources and manufacture the delicate components that need to be manufactured at the bottom of a planet's gravity well?