In response to the OP, I've long wanted to have a more multi-racial fortress, and made mods that used different castes to make different civilizations have several different interbred breeds of creatures. (So dwarves and minotaurs and spider-like aranea and other cave-dwellers were part of the cave civ, for example.)
I made tokens for a naga playable race, as well, years ago. Nagas are capable of bursts of speed and have great strength when grappling with their tail, but have poor endurance, and their tails are difficult to armor. I made them more social and more vulnerable to alcohol, as well. (In fact, I couldn't stop tweaking nearly every personality trait, so there's a lot of subtle differences.)
In response to some of the responses I skimmed over before posing this, I prefer having procedural diversity upon base races to raw wild random gibberish. Too much randomness creates so much noise no signal can be inferred. By contrast, setting up the game so that a human civilization that starts in a desert winds up adopting different cultural norms than a civilization that started in a forest makes for something interesting than blind randomness.
There's a difference between procedural generation and just being random. Procedural generation is only really doing its job when it seems like something a sane person would have made. The language-constructing aspects are still beyond anything I expect a solo programmer to ever be able to accomplish, but when you look at how worldgen works to create an environment, it clearly has rules that try to create a meaning to the way that the world is laid out. I'd rather see the effort spent making it so that civilizations can have distinct cultural differences added to whatever they start out with in a base race, such as skewing cultural values to be more warlike if a civilization is subjected to perpetual struggles for survival, or having a civilization that subsists mostly on fishing or herding have more individualistic set of cultural values than a farming civilization whose peoples are more sedentary.