Nice, I will have a look straight away.
Some more suggestions, in case you ran out:
What do you think about explosions? Giving the chemist something to do, building bombs with large AoE effects. Possibly for catapults and ballista, maybe for special ranged weapons.
Or an Organ. Steam-powered instrument building that gives AoE buffs.
Observatory. Gives an interaction that targets a unit of any invader race on the map, does nothing, but has an TARGET_VERB, so the combat logs shows something. "Gnome uses observatory" "Kobold thief has been spotted". Players could check for thieves, kidnappers and ambushes, without actually revealing them.
Dfhacks regrowth and regrass also comes to mind, since gnomes are linked to nature. You can regrow all grass and saplings into trees, or insta-grow the seeds in farmplots.
Weather control. I wrote a pretty basic Orrery for the Warlocks, but the theme would even fit the gnomes. Dont know if you want to use this, but it allows starting rain, snow or clearing the sky. A bit inspired by the dwemer orrery in Tribunal for Morrowind.
Siren. A steampowered alarm siren that wakes up sleepers/stops breaks. Its just a reaction that calls the "siren" script for dfhack, I use it on the garrison on dwarf mode. Obviously fits gnomes as well.
A factory, which produces metal items in batches and uses no skills. If you dont assign a skill, the reaction finishes instantly, but the product has no quality. So you can churn out low-quality armor and weapons, or any item really, very quickly. Needs power, obviously.
Unique trap components, like the AoE one I posted yesterday.
EDIT: Does your itemsyndrome show any red errors? I still have them in my dfhack window. If you dont have any, could you please send me the version you use atm?
EDIT2: Last suggestion for now: Maybe the gm-editor allows to add GLOW_TILE to creatures on the map, which makes them visible through the fog of war. If you have an unexplored cavern, and a creature in it has a glowtile, you can see it, even if everything else is black. Would make a good "gnomish sonar/radar" thing. Or nature sense. You wouldnt see the creature, only the glowtile, so its just a red '!' or something. But I dont know if the gm-editor can do that... but I use glowtile on fireflies and glowfish/frogs to show some caverns already, that trick works for sure.
EDIT3: Graphics are missing. ^^