Unfrozen

[Moggers]

Dustwalkers are really cool, whats in the way of adding their chilly counterpart- the unfrozen?
And while we're at it, what about manikins?

[Ealb]

They could be added, but there's a couple of problems (conceptual and practical).

• Dust Walkers represented a new nation type that was marginally present in Dominions but not properly present - dynastic-period Egyptians. Visually, adding them (and corresponding humans) was a natural expansion. Unfrozen don't have the same appeal. Admittedly, if barbarians/tribal humans were added alongside them, that would have the same sort of synergy and could work.
• Dust Walkers have in their fluff a very explicit description of a culture that basically amounts to "we're dead, but we're gonna act like we're a bunch of materialistic bastards who are still alive", so they fit cleanly into Dominions mechanics in terms of wanting gold. Dust Walkers demanding recruitment cost and ongoing pay makes sense in a way that doesn't work for a lot of undead - which is why there's only maybe 3 recruitable undead types in vanilla (Nazca mummies, Ulmish ghouls, Scelarian vestals). Still, this could be weasaled around either by adding fluff or doing shenanigans with higher recruitment costs + no upkeep (expensive reanimation rituals) or higher resource/recruitment point costs + no cost/upkeep (labor/material-intensive reanimation rituals), so it also could work.
• So the biggest problem: dev burnout. Right now, the main content dev for the Dom4/Dom5 period (me) is pretty burnt out and not doing much more than picking at things.

[Moggers]

Is the process for adding new nation types documented?
The "unfrozen as an undead but still functional society" problem could also be resolved by implementing them as an ermor-like nation rather than a traditional one.

[elmokki]

The thing with Ermor-like nations and NationGen is that you'd want a considerable amount of randomness and some loose sense of kind of balance. The last time I considered it it felt like a waste of time to add code.

Anyway, I don't think there's any documentation for adding more nations. That said, it is not terribly complex unless you want to make complex things. Basically to start, you can make a copy of one of the files in /data/races/ and add a line corresponding to it to races.txt. Then you can go look at poses and see that they consist of lists of items, and that items are pretty much just picture with indicator whether it is armor or weapon and what id the game should use for it, as well as stuff affecting the probability of the item appearing. I haven't really taught anyone and yet multiple people have made content for the program at some point!

[Ealb]

As Elmokki said, it's relatively simple to make a simple NG nation type. There's a HUGE amount of complexity you CAN use, but very little you need to. Having said that, though, making complex nation types can be a lot of work and in some cases for some types (like freespawn nations or UW nations, to name two) the engine doesn't support adding them. But for straightforward races, it's pretty simple to figure out how they work. I'm going to recommend looking at... hmm... Avvim or Oriental Humans as neither of those bother with themes and are pretty straightforward with their structures. Firbolgs are a fairly clean-cut race that does use themes if you want to fall into that pit. But at a base, you need to define a race file, define one or more pose files referenced by your race file, define the item files referenced by your pose file(s), make the graphics referenced by your item files, add your race file's declaration to nationgen/data/races/race.txt, add your pose file(s) declaration to nationgen/data/poses/poses.txt, and that's probably it for a simple (themeless) nation.

nationgen/documentation/special_commands.txt and guide_to_chanceincs_and_themeincs.txt are definitely things to look at if you want to try this.