While correct about searching for things that have been discussed a ton before posting, I'll note that the slavery-vs-dwarf-ethics things is negligible since cultural ethics will be derived procedurally in time.
As I (probably mis-)understand it, it'll either be "NPC races" that get that treatment (like the sheer amount of variation of night-creatures, and their soon-to-be-realised syndrome collection, as a kind of follow-up to the FBs, et al), or there'd still be a "range" of possible moralities, so that one Dwarven civilisation might consider it a Capital Crime to use slaves, whereas another might "really rather not"... And, like finding the 'civ that
hasn't failed to work out how to make High Boots, when given a choice, it might be similarly necessary to find the Dwarven 'civ that has sufficiently compatible morales with the human 'civ so as to be able to trade with them rather than one or other of you getting the hump over some slight. (Or, conversely, aiming to get a pre-annoyed potential trading partner... If that's the way you roll.)
I'm pretty sure, though, that while toady could make it all an absolutely procedural "%RandomlyGeneratedRaceName% Fortress" game, there certainly are (at present) a number of things that are constant. And even if it's open to changing, I'd still advise that for the foreseeable future it's probably a given that any change to the slavery-moralities of the dwarfs (noting that I've mentioned it in the past, myself, although usually as just one option in something like a creature-driven power source) almost certainly isn't at the top of the agenda.
Later, maybe. By which time all the current suggestions are
probably going to be significantly out-of-date anyway and largely inapplicable without a lot of new thought.