How is compatibility with df therapist? This will be my first run of this mod, just wanted to ask in advance.
Fully compatible. All labors used in this mod are easily toggled with dwarf therapist. The one exception is non-medical training workshops, since you cannot toggle those skills at all, dwarf therapist or otherwise. These buildings are better controlled using permitted workers in the workshop profile - left uncontrolled, any idle dwarf will go train there if training is queued as a task. In the case of the obstacle course, that may actually be for the better.
Perhaps an alternative to cats for pest control? You could have one in addition to cats, but it could be more effective at vermin control and perhaps be less of a cute pet to give dwarves happy thoughts. It wouldn't be an upgrade, just an different choice. Faster perhaps, or flying, or both? Perhaps some dwarves could find them ugly or dislike them, to further balance them.
Of course, a *more* likeable pet, with less vermin hunting ability, could also be possible, something with universal appeal and some happy thought generation but no other utility.
Very possible. I can get started on something to this effect very shortly.
Neither of those animal options would really change gameplay that much, but would offer a little variety in options for fort happiness and pest control.
Perhaps some additional subterranean animals that are tameable by dwarves? Or edit some of the creatures that already exist for that purpose? Giant worms, beetles, cave crabs, axolotl, bats? The pest control animal could fit here too I suppose. These would be largely meant to be improvements over basic animals that fill the same role. Livestock, resource production animals (wool, milk, etc), pest control, or war animals for defense. Since they are more dangerous to acquire they could be more efficient or powerful. This means that trapping, animal caretaking, and animal training would be a more important skill, and would effectively have a tech advancement option. Perhaps upgraded mechanisms (or another advancement) could be required for the traps to capture these creatures?
That last bit, unfortunately, requires new furniture and trap raws (which are not possible right now). The rest of this suggestion is both very possible and very constructive. Given a little time, I think I can get some first generation creatures that fill these roles.
The early attacking but poorly equipped race possibility you mentioned as a possibility earlier would be fantastic. Since Bog trolls have moved to be a later threat, this would maintain an early (but not necessarily overwhelming) threat to work against early forts, without giving them much in return if they defeat them (no free items from weak enemies to sell or melt). Perhaps this is the plan for the moroii, but it sounds like they're meant to be an interesting addition and optional way to start the tech tree (which is a great idea, thank you!). If you have to breach the underground to see them, chances are they couldn't really be an "early threat" to work against. Ideally, this threat would be mostly able to be defeated by caravans without aid, so it would mean using wood, bone, obsidian, and leather items (or common metals) early would be useful for starting a militia and/or traps, rather than just waiting until a supply of iron or steel is available. This effectively increases the amount of metals and weapon/armor materials in the game without having to add them in the mod, since (to my experience) no one bothers making equipment out of weaker materials as a general rule. Perhaps I'm mistaken, but that has been my impression. It forces the player to scrape together more desperate means of combat early. Once they have a trained and equipped fighting force, or simply enough effective traps, this stops being a concern. The idea there is to keep the player on their toes early without beating them to the floor. Just something that would give civilian dwarves trouble, but crude weapons and armor with poor fighting skills would defeat.
I will look into some possibilities here. The moroii are not intended to be a true "hostile" race as much as a curious race that you can interact with (read:kill) as an alternative means of technical advancement. Though they aren't very powerful, they also won't go looking for you - you'll have to dig down to the second cavern level or lower to find them. While I like the idea, the amount of testing involved with each new civilization I add means that this probably won't make it into 0.13 (or at least not into 0.13a), but is a development for the near future.
Another possibility would be splitting the forge so that there are two: a common metals forge and a more powerful metals forge. One that could be used early, for making copper and bronze and the like, and one that requires a minor advancement in order to produce items of iron, steel, or better materials. Perhaps the upgraded forge could simply require more anvils and/or better quality anvils? The means by which this is made more difficult to acquire don't matter that much I suppose. It would be an additional way to force players to utilize weaker materials early and "tech up" by making more anvils or whatever they need to build the next forge. This would also make the player have to choose between outfitting their forces with as much copper / bronze / etc as possible or spending it on teching up and leaving themselves more vulnerable while they build or trade to get the parts needed. The cost to upgrade would have to be significant but not prohibitive in order to achieve that. Perhaps, instead of requiring anvils, it requires some other part made form the basic forge in the same manner that you've used for other tech advances. This would mean that the player would not be able to directly trade for the advancement, and would need to manufacture them, taking and materials to do so. The materials could perhaps be traded for, so that if you were on a map with only more powerful metals you could still use them. For instance, if you started surrounded by iron or mithril but lacked any weaker metal like copper or silver, you could trade for the weaker metals just to upgrade. This would also have the addition of making trade more vital, again encouraging players to keep their forts open for business and defended rather than walling themselves in right away.
Did the "sapper" idea pan out? Can gremlin tags be added to other race castes or creatures that could accompany a race (as trolls do on goblin sieges) to provide that additional threat of trap dismantling or lever pulling?
Anyway, there are some ideas. Hopefully there is something inspiring there.
Forge reactions are hard coded, but hadrine (a new feature of the tech tree that will be in 0.13) attempts to do something along these lines. Voidshard was initially planned to only be available through a complex and dangerous reaction chain using a claimed voidshard item, but this was undermined by the hard-coded behavior of metals to be melt-able at a smelter. Hadrine gets around this because it is technically a typeless inorganic material instead of a metal, but this also means that hadrine cannot be used for anything outside of the few specific reactions designed for it.
I have attempted to stagger the metals by making high-level metals (iovium, mithril, damascus steel, ether, voidshard) much more difficult to obtain than simply smelting an ore. Iovium requires extra fuel, and is extremely scarce. Mithril is fairly rare, but also highly impure, requiring four ore and five reactions to produce a single combat-grade bar. Damascus steel is only available through a complex reaction chain, involving the smelting of iron into pig iron, the smelting of steel using pig iron, iron, and flux, and then the alloying of steel with vanadium (which also has to be smelted). Ether is a chance product with all of alchemy's associated risks, and is unreliable when trying to outfit more than a single unit (and it also can't be used for armor). Voidshard is simply melt and then forge, but you'll have to liberate it from its extremely vicious owners in order to get your hands on it. Adamantine is the ultimate risk-reward, because mining it runs the risk of dooming your entire fortress (if you're not very, very, very prepared). Hadrine will fill a role somewhere in the ballpark of ether, except it is only available for two unique armor pieces, and requires a LOT of tech advances and reactions to produce. Hadrine armor is the most protective armor you can get short of artifact Adamantine plate mail, but it is also very, very heavy.
I feel that trade caravans already play an important role, because they can bring limited quantities of these materials when you do not have the capability to make them yourself. The dwarven caravan can even bring orichalcum for the first tier tech tree advancement upon request. I expect further developments in the caravan arc, including the reimplementation of wagons, to make these even more important opportunities. A single new token could open up an entire world of possibilities. For example, a token multiplying the price of trader goods would allow me to create a race that could "sell" tech advances for exorbitant prices without causing weird side effects of toggling the actual item's values... Actually, scratch that. I just had an idea for a roundabout way that I can accomplish a similar effect in the current version. Woohoo, another idea for 0.13 (or maybe 0.14). Unfortunately, buying one of the items would not devalue it, but this could be a built-in mechanism to discourage buying too many tech advances, lest the voidwalkers come knocking a bit sooner.
As for sappers, I have put together a special caste of lizardmen to fill this role, though I am unsure how well the AI will utilize it. It will probably not make a noticeable difference in sieges, but thieves of this new caste arriving at the same time may be able to get through and cause mayhem... Or open your main gates, if you're not careful.