Well, the Wizards of the Coast are getting ready to release yet another expansion of cardboard crack (Magic: The Gathering) and a certain type of critter from the setting has caught my eye: A diverse group of mechanical beings called Myrs.
Here's an article that gives a good overview, with pictures. (Some text can be moused over for more card images.)
I like the idea of being some unseen artificer commanding these beings to make megastructures in my name. A while back I contemplated the idea of having some sort of mechanical golem race, but I think Myrs would be more interesting to design, since they could be broken up into many castes, if I understand the creature tokens correctly.
Anyway, I'd like to do a bit of brainstorming and hopefully get a bit of help from some of you modders who know what you're doing.
Stuff to address:
1. Inorganic perks: It seems pretty natural that Myrs wouldn't need food, water/booze, sleep, and so on. Of course, not needing to provide any of those things would make playing them a lot easier.
Too easy without some sort of balancing disadvantage, such as no natural healing. An alternative that comes to mind is making them require some exotic kind of food/fuel/mana/whatever to keep them running.
2. Making more: A while back, I posted a short lived thread about the idea of building a robot scout creature in a custom workshop. It quickly got shot down because custom workshops can't make creatures. So, how could DF Myrs make more Myrs? Simply birthing more like organic creatures (Queen Myr?) or relying on migrants is probably the easiest answer, but if you can think of other ways to increase a Myr hive's population, I'd like to know about it. (...Could caravans trade new Myrs to you?)
3. Castes: I'm not going to insist on making a caste for every Myr card (especially since it'd be impossible to translate most Magic mechanics into something for DF), though something like small workers, big soldiers, smart overseers and such would probably be the most realistic option.
4. Thick skin?: I'm not familiar with the fine details of DF combat, but being made of metal has to have some pretty good advantages... Though Myrs seem to often be made of lower quality metals given the cycle of mana producers: gold, silver, lead, iron, copper, palladium. I don't want things to be too easy, so this sort of thing might need testing and balancing in some fashion.
5. Myr culture: Since they'd technically be a civilization instead of a bunch of mindless automatons carrying out my whims, I suppose there'd be some need to define things like their ethics (or lack thereof) and what makes them happy or unhappy. For relations with other civs, Elves seem like a natural enemy since Myrs would view wood as just a convenient source of combustion for the forges.
I'll be looking over the wiki for inspiration and better ideas about what's possible.