One thing it might be good doing now is some "wildlife" cive entity tags.
For example, to be a bit egocentric, my giant hornets use current [FOREST_SETTLEMENTS] from elves, so that they won't have buildings, however this should not change at whatever future point elves get magical giant trees to live in, I think it is fairly reasonable that there is a tag meaning NONE for building construction.
in the same line it might be a good idea to have a simple nomadic civ whit appropriate tags, it could just use the same human creatures as the plains civ does, basically it would have more migrant groups that never settle and no sites.
What also would help moding is custom names for sites, like elves would need to have something in the lines of [SITENAME:forest retreat:forest retreats] and dwarves [SITENAME:mountain hall.:mountain halls].
What would also be good and job should MOSTLY be a copy-paste (of coerce you can never know whit Toadys code...) is to make a professions/skills to use custom names like the dwarves currently use to call XXXmen for XXXdwarves (fisherdwarves and swordsdwarves for example).
Also for future [animal]men civ (and so peaple won't complain I only suggest things I currently need myself in moding) already now adding a chasm choice to the biomes might be good.
On a unrelated note should not some of the venoms that currently stun/paralyze victims rather/also cause pain? I suggest [EXTRACT_PAIN].
I know that you have stated moding is of very low priority, therefor I have tried to come up whit ways these could be useful in the vanilla game, also due to the new moding subforum, useful lists posted there and mentions in the devlog I thought you might have partially changed your mind about that, if not I ask of forgivingness.
These would be very useful however. Please? *puppy eyes* [<- unskilful attempted guilt trip]
Your vision is the most important thing however, and suggestions that contradict that I don't want you to listen to, even if because I misinterpreted it they came from me.