If you have played anything other than a pre-generated character for any RPG system featuring multiple race options you know something about racial traits. It puts the pointy ears in elfs, beards on dwarf chins, and humans… well, makes them versatile.
Racial traits help us to understand what makes fantastical races fantastical how that can be reinforced in-play at the table. In some systems it goes as deep as altering a character’s core abilities by boosting some stats and reducing others.
This is however a double-edged sword. By having racial traits as a fundamental foundation for the modern RPG system it constantly reinforces the racial tropes as developed by the originator of modern fantasy, Tolkien. Dwarves live underground and deep halls of stone and are renown artisans. Dwarves in RPGs as a result have dark vision, can keep from being lost underground, have a bonus to spotting something strange in stonework, and often have an innate ability to appraise the worth of items such as jewelry, arms, and armor. This can go further to racial weapon training with hammers and axes. Dwarves are slow but steady on the move. They move with equal with speed whether naked or loaded down with 200 pounds of war regalia and gear.
Just from the above passage we can draw some broad stroke assumptions as to how dwarves are represented regardless of a game’s particular campaign setting. If the campaign has a multitude of underground dungeons and ruins dwarves will be some of the best and most common adventurers. Their dark vision, ability to tell direction underground, and better ability to spot inconsistency in stonework makes them unparalleled underground explorers. In addition their unencumbered speed, and racial proficiency with heavy weapons makes them ideal as hard-nosed fighters on the front lines. This idea is better compounded with rules systems choosing to give dwarves a penalty on dexterity stats while boosting either their strength or constitution (the two most useful stats for front line fighters).
But take away underground dungeons, perhaps this new campaign will feature exclusively topside adventures over an expansive landscape and most actions will happen during the daytime. Dwarves because of their particular racial traits become far less useful. Dark vision is far less useful, underground direction sense meaningless, and stonework perception only useful for the occasional hidden passage or hiding hole in a wall.
Dwarves are just one example. We could run down all the different races and sub races but you get the point. So if you decide to run a new campaign these are issues you may want to keep in mind. In doing so it may be worth offering some alternative racial traits to replace those which will not be overly useful in your campaign’s setting. A quick look through the race entries of your current system and some time thinking about the plot of your campaign’s arc should give you a good starting point for developing alternative racial traits.
Past character generation in a campaign, racial and class abilities fall to wayside from the perspective behind the screen. They are locked down as defining features of a PC, tools for the player to use in their time adventuring and nothing more, other than boosting the ability with a feat choice. This is unfortunate and as a Gamemaster you should not be lulled into complicity with any facet of the game. This can be a quick and dirty way to add some really interesting ideas into your campaign.
Mutation 
Generally we consider mutation something only found in more modern settings and ideas like TMNT. In D&D 4e an attempt was made with the changing landscape of Forgotten Realms and the Spell Plague to include mutation ideas. Unfortunately they never took root, mainly because of poor design integration. A quick look of cost/benefit evaluation shows most of the Spell Plague powers required characters giving up too much to make the mutations worthwhile options.
Mutation can however be a good way to grant a boon or lay a lasting curse on a character. During an arc run in a home brew campaign setting the party unintentionally helped a witch with a dire ritual. To repay the characters she left behind dark gifts. To reinforce the terrible nature, not only of the potential gifts but the people they were dealing with, these dark gifts were hidden in the bowels of the witch’s servants, found hanged by the neck in her den stomach’s wan and distended with the boons. All the party decided to forgo the dark blessing but for the assassin PC.
He gained the boon of shadow for his macabre effort. The PC gained near supernatural ability to hide in shadows (an incredibly useful power for an assassin). The trade off was he suffered light sensitivity, a heavy penalty while attempting complete tasks and attacks while in bright light. The result being the PC was confined to be a shadow dweller and the stigmas associated with that habit.
To keep things roughly balanced you will want to have a good bonus offset by a penalty. I used the duplicity of the boon to make light a far more important factor in the campaign than it was otherwise. If you hand out some powerful boons look to offset it by having the player lose a racial or class trait as is appropriate.
Using mutations and special training boons to replace class and race features will give you some extra options as alternative rewards for the party. Using mutations can help to make PCs feel like they are shaped by the campaign setting in which they live and helps to makes the PC a little different than their racial boilerplate.
I believe as DMs and players we need to find ways to deal with racial traits in unconventional ways.
I like taking players out of their natural environment (like keeping a dwarf above ground, even in a forest) and finding ways to be creative with who the character is to overcome any limitations. I also like playing characters that are limited or unique in some way. These types of situations can create some of the most memorable experiences while playing.
With the dwarf, are there ways to be creative with his love of stone and being underground that can still be useful outside of dungeons and subterranean cities?
I also think reskinning and tweaking in the way you described is a great way to add flavor to the game. I appreciate what we did with our “elven urban rangers” recently. These elf rangers enjoy the city so much, they lost their natural nature training for streetwise, and one role plays as uncomfortable adventuring outside a well established city.
Fish out of water works well. The problems arise when the fish is always out of water. That’s when a temporary impediment can become a permanent limitation. No one wants to play a character that is always bad at a common task in a campaign.
To improve on the dwarf we have to restructure the way we think about them. Maybe his love of stone becomes ace knowledge of geology, engineering, or another discipline more useful to the campaign. Just thinking about darkvision, if your dwarves aren’t underground darkvision means they’re nocturnal. Having an above ground, common, race as nocturnal wildly shifts some paradigms. Hours of operations for shops and markets including a statistically significant population will now shift into high gear around dawn and dusk rather than midday.
If you want to get extra fancy PC and NPC dwarves continually out in the day instead of night may suffer from shift work sleep syndrome.
I love solutions to mechanical problems that occur within the story or narrative, just like this. It’s one of those ‘aha’ things that make RPGs fun.
Your use of the shadow boon is really cool. I’ll look into testing something like that in one of my games.
Awesome, let me know how adding boons works out for you!