It would be interesting if some dwarves had allergies...
For instance some might be allergic to shellfish, or they are lactose intolerant, or allergic to bee sting.
If an allergic dwarf has interaction with its allergen object then he will need immediate medical attention or face some problems up to possibly even death. It would give hospital workers something to do when you don't have much fighting going on, plus would add additional layer of challenge in deciding what dwarves go outside as you would want to keep those allergic to bees indoors, and it would enforce the necessity to have varieties of food for those allergic to certain food types.
Secondly, it would be interesting if some dwarves are only gonna eat only plant food products... They can be vegan dwarves and they will get negative thoughts seeing meat products when they go to get food and also get negative thoughts if they witness wild animals being killed or hunted and seeing a domesticated animal get butchered.
Finally, another idea I think would add some more challenge and variety to the healthcare industry are diseases and a medicine industry. If you lack a plethora of soap then your dwarves would be more susceptible to infections and disease. For instance, in the winter a dorf might catch the flu and it can spread in your fort if they aren't quarantined to the hospital early enough.
This could extend into other things such as lycanthropy. Already now exist werewolf mobs in the game. If a dorf is bit by a werewolf he will have a chance to catch the lycanthropy disease. Diseases like lycanthropy can be treated with proper medicine if done early enough, but after a certain amount of time the disease would become permanent on that dwarf, On whatever months is full moon the dorf would randomly turn to a werewolf for that time. If you like the dorf you can just lock him in a room, otherwise he will behave like a berserk dorf but much stronger.
A similar disease is zombie infection. When your dorfs fight the zombie type of creatures if they get bit then they will only live for a month or so and then succumb to death. They will become a corpse for a certain random time and then will awaken as a zombie.