In next update I've added hospital where all sick people will go but plan in the future is that you can also build settlers houses.
Herbs: collecting in the forest in small amount -> herbs add-on to green house -> pharmacy shop -> supplying hospital, cleaners <-> plague and infections, sexually transmitted disease <-> using condoms,
greenhouse should generate much more food, but with significant delay - it is not possible to to grow food within one day, so it may work like accumulator: at first settlement should invest some amount of working days before it will start to produce food
weather: bad weather conditions may temporally stop woodcrafting/hunting, low temperature may increase wood consumption for heating
drugs: involving to business (maybe in greenhouse add-on), delivery by car, or fighting with it by intercepting couriers, moral dilemma, drug users within own guest house, guarded marijuana/coke plantation in the forest (own or enemies)
water: drought, dirty water after rainstorm, polluted water, disease, additional challenges to clean water sources, water balance: each person and building increase water consumption, guests 1 unit per day, slaves 0.3 unit per day