Anybody on this one? Anybody at all?
So the design calls for combat, stealth and trade over multiple eras. That's multiple planets, multiple cities. It's a pretty steep challenge, but I think that story and world design can come to the rescue here.
The storyline I'm going to go with first starts you on a ravaged, recovering earth. A major substory will be the world rebuilding, with the increasing appearance of "neurozombies," people who have been sequestered by nanotech & modified against their will. This will be a remnant of war tech, as will these huge sandstorm clouds of deconstructing nanites.
Alright, the enemy behind this will be a rogue doomsday AI that's bodyjacking people, creating the huge storms, and generally wreaking havock. It will be driven from the earth, and flee to space, where it's tracked down and destroyed. But not before it secretly scatters itself to the stars on clouds of nanites launched near the speed of light.
What does this do?
The result will be tens of thousands of "vehicle" characters, people who were forcibly downloaded into machines. These people will opt to become a culture of machines in space, transferring to probes and rovers and even large ships.
The rogue AI's nanite clouds and constructs will make an appearance on other planets. On Earth, the threat will start out balanced. But out in space, you may encounter fleets, sprawling factory bases, or even dust clouds where planets uses to be.
I would LOVE to be able to procedurally create aliens like Spore will do, but that's like wishing for a Lear Jet when you're homeless. However, I'm going to search high and low for graphics genuises that can help me populate planets with aliens and creatures.
One thing that MIGHT work is to simply accept that there will be four or five body types, and then try to scale the animations, vary the textures procedurally, and use attachment points for things like horns or tufts. It won't be anywhere near as varied, but a little is better than nothing.
Ultimately, I'm seeing four types of environs for enemies:
* Human cities, with bots, humans and later aliens
* Alien outposts, with aliens, bots and humans
* Land frontiers, with bandits, colonists / survivors (if on Earth), and possibly creatures or rogue AI constructs
* Space, with "post-human" probe/ship people as like NPCs in space, and alien and human ships with crews
If I can get a few scalable, reconfigurable animal body types going and mix and match human machine pieces, that should be enough variety.
I hope, that is...