Just brushed up on the rules...
PHB 190: The space of another creature, whether hostile or not, also counts as difficult terrain.
PHB 191:You can move through a nonhostile creature’s space. In contrast, you can move through a hostile creature's space only if the creature is at least two sizes larger or smaller than you. Remember that another creature’s space is difficult terrain for you. Whether a creature is a friend or an enemy, you can’t willingly end your move in its space.
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I'm thinking something like this...
[SECTION]Martial Alacrity. Starting at 2nd level, you can move through the spaces of hostile creatures, regardless of their size. Doing so acts as difficult terrain as normal, and you can’t end your turn in a creature’s space.
Additionally, you can use your Reaction when you roll initiative (as long as you are not surprised), roll a saving throw, or an attack hits or misses you. You can use this Reaction to interact with an object or feature of the environment; for example, you could stow your sword and draw your bow, open or close a door, throw an unconscious ally over your shoulder, hold open a portcullis, withdraw a potion from your backpack, remove a torch from a sconce, etc.[/SECTION]