With the villain update, if a goblin from a goblin civ obtains the title of king over a human or dwarven civ through a coup and intrigue, will that civ then start to act more similarly to a goblin one because of the goblin king's values, which originate from a goblin civ? For example, will a human/dwarven civ that is ruled by a goblin from a goblin civ be more likely to declare wars?
Do war declarations, etc depend on the values of the actual ruler or does diplomacy right now depend on the civ's average values instead?
Yes, the goblin's core personality from its own civ won't change without some emotional introspection, only second generation citizens in a foriegn nation commit to a full value flip to go 'native'. So if the evil goblin monarch kicks the bucket and their son born inside the Dwarf civ (with marriage to a refugee goblin for example) is named heir the neo-dwarf goblin is still going to have a terrible temper and murderous disposition, but they'll have dwarven ethics. A beard too most probably.
The kind of not cavalier but often aggressive attitude of goblins will brush up against other civ leaders and prompt them to go to war more often, especially since they're often not as charismatic as demon leaders either especially if they favor dreams of power, enjoy violence and prize martial prowess. Though some civs just declare wars because goblins are liars and decietful. (pretty scandalous for dwarves)
Actual societal change won't occur until the law arc where its scheduled, but a untoppled immortal ursurper can still destabilise the kingdom in a single lifetime.
Actually, facetious as my earlier comment about boats was, given that wagons are considered to be creatures, is it actually possible for the procedural body-horror abominations to incorporate wagons?
Undoubtedly same as the lawnmower modification, if there's wagons in your livestock by some odd means (probably a bit of deliberate poking around) it can probably happen, otherwise id think its just wierd.