I am creating a race of Mutants for my dark fantasy campaign. The core racial mechanic is that each Mutant character picks two mutations from a list. Each mutation gives +1 to an Ability Score and a special trait. Special traits are supposed to be equivalent to ~two thirds of a Feat (I am trying to power-match them to Humans with Optional traits).
I was thinking of one mutation that would give a form of Reach to the character:
Stretched arms: Your upper limbs are flexible and are, or can become, extremely long (e.g., multiple joints, extensible, tentacle-like, etc.). As a bonus action, you can enter in reaching stance until the start of your next turn. While in reaching stance, you add 5 feet to your reach when you perform a melee attack, as well as when determining your reach for opportunity attacks in melee. Your Dexterity score increases by 1.
Instead of giving a permanently increased reach, which seemed potentially too strong to me, the character has to spend a bonus action, which means: (1) it needs to be activated; (2) it gets in the way of other powers (such as off-hand attacks, second wind for Fighters, etc.).
Does this seem balanced?
It's been pointed out that the Bugbear playable race in Volo's Guide to Monsters (p. 119) has the trait:
Long-Limbed: When you make a melee attack on your turn, your reach for it is 5 feet greater than normal.
So the character would always have extended reach (no need to spend a bonus action), but only for attacks (not attacks of opportunity). This might be a good and more official replacement for my previous tentative formulation (and I assume that being in an official supplement it should be relatively okay in terms of power).