This is wishlist of a bunch of things I would like to see in future updates, especially stuff that I think will be necessary for the myth and magic update or related to it, or would just be really cool to have in general. A lot of it is things Ive been trying to emulate with my mods currently, and things Ive come up with over the years that I wished I could do.
In no particular order;
1. Interactions and syndromes as a direct product of a reaction. In effect, completing the reaction applies the syndrome or interaction directly to the creature that performed the reaction, instead of creating an item that interacts with them in some manner. This is possible currently only through items that boil and must be inhaled, or must be eaten, or via lua scripting, requiring DFHack integration.
2. Interactions/syn_class as a reagent of a reaction. This would mean a reaction can only be performed by a creature affected by a particular interaction or SYN_CLASS. Currently there is no way to do this that I am aware of.
3. Syndromes accepting affected/immune syn_class strings, such as "VAMPCURSE," so the syndrome of a creature's venom explicitly targets/ignores creatures affected by a vampire curse interaction. SYN_CLASS and CREATURE_CLASS are not interchangeable and although interactions can affect/ignore both creature classes and syn classes when targeting, syndromes that aren't tied to an interaction cannot, so you cannot for instance make all vampires immune to the venom of a particular creature by making "VAMPCURSE" an immune class for that creature's venom.
4. Allow defining a "use" interaction, like one would 'i'nteract with die or codices in adventure mode, for various item definitions like armor, weapons and tools. upon use, a particular interaction is begun as if the creature had used a natural ability or acquired power, and the user can select a target. Could also apply an interaction directly to the creature.
5. Similarly, allow defining an interaction to be applied to a creature simply holding, wielding, wearing or possessing an item. Say you pick up a type of tool, you get an acquired power or curse. Preferably being able to define if this is permanent and retained after dropping the item, lasts for a certain period of time, or only while the item is in your possession.
6. The dreaded ever-present suggestion I know everyone else has made before: Apply syndromes from an item if a creature is struck by that item type, or material, as an attack against them that landed successfully. Stabbing them with a special dagger that causes them to turn into a kobold, a sword made of "fire" that causes a target successfully struck to experience burns around the wound etc.
7. A similar suggestion, allow defining a material syndrome with additional infection vectors when held or worn, including from solid objects being carried.
8. Creature/caste token that automatically applies an interaction or syndrome to a creature, with variables including percent chance of the syndrome or interaction being applied, time after spawning after which or age of the creature upon which it will be applied, without the creature needing to take any action. This can currently be kinda accomplished by making the creature leak a fluid which affects it or giving it an on-self interaction, but neither method works 100% in all situations, making them leak a fluid for instance causes them to constantly try to bathe or they may not choose to use a power for an extended period, and of course age of the creature cannot be taken into account, so children can gain magic powers for instance, when you'd rather restrict those powers to adults. (Like kids stopping to fling fire balls at invaders instead of running away)
9. Syndrome tag that allows it to interfere directly with another syndrome or interaction of a particular class. Reducing or extending duration, severity, or ending that syndrome targeted. This would allow for, for instance, cures for werecurses or vampcurses, poison antidotes that stop a particular poison's ongoing effects, or even a syndrome that amplifies the effects of another, but does nothing on its own.
10. Summoning interactions, like those found on the slabs of demons in vaults, that summons a particular unit over and over. In this case, not a particular historical figure, so not everyone trying to use the interaction summons the same guy causing them to teleport across the world. But instead, the first time the interaction is run by a unique historical figure, it uses the summon interaction to generate a historical figure, now tied to them, that they summon. Every subsequent time they use the interaction, it summons the same historical figure again. If they were still alive, it summons them including all the items they carried on their person. If they were deceased, it resurrects them. This can be used to make permanent familiars that can be summoned, always conjuring the same unit and maintaining their traits and identity, and persistent inventory, instead of creating new units every time.