Plagues and other great diseases are important parts of history and some settings. They defy man and may even defy God in their swift and terrible punishment upon the body of society.
My issue with modifying/removing dwarves and elves is that the PC’s may want to play them.
One of the most powerful tools found in the World Building 102b article is the Worksheet. Here is a place to put the settings you might make with them.
Far to the north amidst the endless ice-flows it is rumored that a dwarven Walrus Totem clan exists. These rumors have been unsubstantiated to date, unless the dwarven sage Glurt Goblinguts is to be believed. He claims to once having encountered a troupe of huge dwarves, each standing a beard’s length higher than the tallest known dwarf. These dwarven “giants”, their hairy chins crusted with frozen shards of ice and dirt, hauled gargantuan yellowed horns or tusks upon their wide shoulders, and their helms, likewise, sported massive, down-ward pointing tusk-horns. Glurt Goblinguts later speculated that the impressive size of these dwarves was most likely due to their arctic diets, almost exclusively fat-based.