...is there a particularly good guide to editing the DF raws floating around?
Search the magmawiki... Bah, OK, here:
DF2010:Modding guide. Also, be sure to check out
Shaostoul's Guide wiki (click the [show] tabs to unhide the rest of the page) and the
Shaostoul's Modding Guide thread. And if you have any questions (preferably ones not already answered in these links), you can ask in the
0.31. MODDERS WORKSHOP (NEWCOMERS WELCOME!) thread.
What determines who your "neighbors" are? If you're a long distance from other civs, will it affect the reliability of caravans and migrants?
It was my understanding that distance is a factor. But how much and to what extent, I'm not sure. (Search the wiki.) However, it is known that if you embark on a small island with no civs as neighbors, you won't get any caravans or sieges. Both of those need access to your island on land. (Though, I have read a claim that it is possible to build vast stretches of roads and bridges to said island - possibly requiring several separate embarks - in order to give them access.)
Are there any simple ways to encourage war between civilizations in world gen or does it require modding?
Depends on what you mean by "simple". It should be possible to get certain civs to fight each other by actions of the player in Adventure Mode:
DF2010 Talk:Adventurer mode > Thoughts on Elf AdventurersBased on reviews of the Legends logs, attacking (or being attacked by?) members of a given Entity seems to make that Entity an Enemy of any Entities your adventurer belongs to. While I haven't tested this, it would seem possible that this could cause your civilization in Fortress mode to be at War with someone on embark, if you made some enemies with a dwarf adventurer of the same civilization.
DF2010 Talk:Adventurer mode > Starting wars?Can an adventurer cause wars by traveling around and attacking peaceful civilizations? --TomiTapio 18:27, 6 July 2010 (UTC)
Sort of. If the civilizations aren't already at war, they won't call it war. But if you're allied with one and cause trouble in another, they will name anyone you attack or who attacks you as an enemy, who will become a quest target. You could very easily make this snowball into a chain of aggressions from your allied nation on the ones that you're attacking. Even better, if you bring companions from your allies into settlement that has declared you enemy, they will run completely amok. This could be any nations at any range, whether they have any good reason for war or not. DokEnkephalin 17:09, 9 September 2010 (UTC)
Once you've gotten them fighting, you could retire your adventurer and switch to Fortress Mode to see if it sticks.
...what happens if you constantly reject, kill or seize from the mountainhomes caravan?
Rejecting them I think gradually upsets them. But arranging an "accident", such as a flood of water or magma is not the same thing as having your dwarves attack them directly:
What are the penalties for killing dwarf merchants/guards?
Depends on the method. If you flood the depot or use some similar indirect method, then the mountainhomes will just send you less stuff next year because profits were so bad. If you use kill orders, you'll cause a loyalty cascade. Basically, the dwarf that does the deed will be labeled an enemy of the civ but will still be a member of the fortress. Thus, other dwarves will flee/attack him because he is an enemy of the civ, but if a dwarf succeeds in killing him they'll be killing a fortress member, and will become an enemy of the fortress. They will, in turn, be fled/fought by the other dwarves. That cycle will repeat until everyone is dead. From personal experience, it is quite amusing and is a good way to end a fort you're bored with.
What if I drive them insane first by locking them in with a drawbridge?
That is a very good question. My gut says that if they go berserk they will no longer be members of their parent civ, and will be fair game. I'm not at all sure about melancholy/babbling though. I propose SCIENCE!