To-do (with the stipulation that I won't likely be doing these things quickly):
1. Make the dwarves less humanlike. I envision the drones being armless and having more than two legs, now, almost like beetles, with a mouth that can grasp. Other castes are going to be a mix of insect and humanoid, to the point that Royals look like normal dwarves, but Blood have two arms, two pincers. Gender limits are going in also; I suspect that Blood and Royal dwarves will be the only females in the hive.
Noble definitions will also get redone. Militia commanders and captains will have to be female, in order to limit it to Blood and Royal castes; if this works, it'll mean that you need these castes to even form a military. Mayor, baron and higher won't exist, but there will be one Hive Queen; no mandates for any of the nobles, but they'll have a high value room requirements and the ability to make many demands.
Also, I intend to cut the Hive off from caravans - I'd cut them off from migrants too (to avoid a number of minor bugs), and up their reproductive and maturation rates, but there's no guarantee that the player will get a breeding pair on embark.
2. Add in Hive reactions and crafting. One issue that has occurred to me is that a lot of jobs can easily be done by Drones; who cares if they have no skill if they smelt at 300% speed? To combat this, I intend to make some reactions for skills that normally are just performed faster when skill is higher; these reactions will instead produce useful objects with a quality attached.
Is it possible to have the quality of ingredients affect the quality of the output product? How?
For Hive metal, I want to require the player to collect Blood and Royal Jelly. Right now there's no way to collect blood except to either embark with it or import it; I need to add a reaction. Right now I'm intending to have it be at the Screw Press, resulting in a <species> press cake and a barrel / jug of blood.
Hive armor would include Carapace Plate and Jointed Helms. Trap components would include Razor Wire and Crushing Maws. Weapons include the Wafer Blade (pressed), Hive Stinger (a knife that uses wrestling skill), Farsting (crossbow skill), Razordisk launcher (bow skill, pressed coins for ammo), and Longsting (spear with very thin point, low stuck chance).
3. Other species. Ideally, I want to have regular dwarves as a hostile and very dangerous opponent. After all, the Hive is monstrous, and its ethics (to be defined in step 1) are completely callous towards anyone outside of the Hive. On top of that, I intend to add some powerful castes to other opponents, and maybe add a couple species, including the deadly Collectors.