However, the effects of these scenarios were fairly boring. With no historical dwarves in the world the game just rolls random migrants and the fortress proceeds as usual, except with citizens that have no earlier background or relatives. Even caravans and liaisons seem to just poof into existence when they are needed.
Is there any way to avoid this? That's my biggest problem right now... caravans and migrants coming to existence without a civ around to support it.
I can make sure I get no migrants and caravans... but not without cutting off all the caravans for other races, which I actually want.
You could just use a pop cap of 1 in init for a simple way to stop migrants, which is easy.
For caravans, you need to get more tricky. You could disallow dwarves from using [COMMON_DOMESTIC_PACK], [COMMON_DOMESTIC_PULL], and [COMMON_DOMESTIC_MOUNT] in the entity_standard raw. This disallows horses and things at embark. Then take away [DIPLOMAT_BODYGUARDS] and [MERCHANT_BODYGUARDS], as well. Maybe all you really need to do is take out the ACTIVE_SEASON tag to stop them from ever coming. You should probably also eliminate or mod all nobles that aren't appointable.
To help ensure dwarfy death, I'd recommend further changing your worldgen parameters. I like to
massively mess around with my worldgen parameters, anyway, since I like having more diverse biomes, so I tend to put variances up to 2000 or something instead of 10.
Anyway, what you want to do is make mountains less common, and mountains are caused by elevations greater than 200. Go to your elevation weights, and make them something like 2x2 and 5:10:1:1:1 with 2000 variance to make mountain ranges tiny and sparse. (The first number is the weight of oceans, last three are mountains, the second is everything else. "Everything else" appears for half of the third number as well, but you get 100% not-mountain if you weight the second number.)
You can change what biomes dwarves will cross when looking to expand their civ by taking away [BIOME_SUPPORT:FOO] tags in entity_standard. You might also want to drop MAX_POP_NUMBER to something more like 100. MAX_STARTING_CIV_NUMBER of 1, as well, better ensures extinction, and lets you spawn more civs of other races, especially things like elves, that tend to like to genocide dwarves if they have a chance.
By extension, go to rainfall, up variance to something high like 1000, and set weights to be more like 3:1:1:4:30, and you'll have a TON of forests. Guaranteed elf conquest of the planet.
Then, you can ensure their demise either through upping megabeasts and unique demons (which create goblin civs) or through just letting the elves conquer. You can increase the odds of making elves conquer by further tweaking their ethics, although that's probably overkill by this point. (Keep in mind, if an elf civ is what destroys your dwarf civ, they will never have declared peace, so you will still be at war. They WILL ambush you early.) Try setting things like LYING or OATH_BREAKING to ACCEPTABLE. (This also changes the penalty of mandates, apparently.)