Introducing...ANDROIDS! Or, uh, synths? I dunno. The point is, I think these could make an interesting addition for people who want to try to play the game a little differently. I like to think it would add something that's not only refreshing, but also challenging. If we are to think in terms of 'difficulty', I'd scale it like this:
Lowest
Humans
Lizardmen
Flypersons
Androids
Plasmamen
Highest
This means that while they aren't quite the 'hard mode' that plasmamen are, they are still rather challenging due to their rather long list of drawbacks. While they DO enjoy a small range of benefits, the negatives do outnumber them by quite a bit. I tried to give them a level of uniqueness that is still balanced.
This spoiler contains mostly lore fluff explaining how I'd imagine an android would be played from an in-universe perspective. If you're solely here for the technical and gameplay assets, don't feel bothered to open this.
Spoiler:
Androids can not have a gender or hair.
They cannot have any other skin color other than 'silver' or 'gray'.
They can have differently colored eyes, however.
They're essentially gray/silver bald humans in terms of appearance. Maybe some darker lines and some lights matching eye color on their sprite? I dunno.
Benefits
Resistant, but not immune, to cold and heat
Immune to viruses.
Does not need to eat.
Can attach limbs from the ground without surgery, though you must remain still while doing so.
Can attach implants without surgery. See drawbacks, however.
Can repair brute damage with welding and burn damage by replacing wires.
Syringes cannot penetrate your skin. Also a drawback.
Drawbacks
Cannot heal brute and burn damage with conventional means.
Bleeds oil, which means that regular blood will NOT help fix blood loss.
Implants, once attached, can't be removed. Incidentally, you can only have one of each 'type' of implant. No having diagnostic, medical, AND security HUDS at once. Just one.
Vulnerable to electric shocks and can be knocked out cold by EMPs.
Not considered 'human' by the AI.
You can't have command jobs.
You can't use syringes, which could be a drawback if it's something positive.
You cannot receive powers through Genetics due to your inorganic nature.
Just because you CAN attach limbs without surgery doesn't mean it'll always work. There's a decent chance you'll fail in attaching the limb.
Organs are artificial, meaning that they will not work for organ donation or transplants. Their brains are compatible with MMIs, however.
Cloning is either impossible or very difficult.
This is obviously still something of an early draft, but I figured I'd pitch the idea to y'all anyways! If you have any questions regarding this suggestion, or any advice on how to balance it further, feel free to let me know!
Hopefully this idea is as appealing to others as it is to me, and I look forward to hearing your input.