Little Fella

You've been living your whole life as the little guy, always bullied and picked on due to being much smaller than others. This doesn't necessarily mean smaller in physical size, but in most cases, it does. Throughout your life, you've learned how to take advantage of that small size in ways many wouldn't even notice until they are taken completely by surprise. 

Note: This is the other Little Guy rogue but with mods added in.

Quick

You have a small center of gravity, allowing you to jump to action quicker. At 3rd level, add your proficiency bonus to your initiative rolls.

Short

You have learned that larger people then to swing a little high. At 3rd level, you may take the dodge action as a Bonus action against creatures at least 1 size higher than you.

Small Hands

As you grew up small, so did you hands. At 9th level, you get advantage on Dexterity (Sleight of Hand) checks when pickpocketing those larger than you. You may use this feature as many times as your level. You must complete a short or long rest for this ability to reset.

Momentum Transfer

Big guys swing REALLY hard, and you’ve learned how to use that against them. At 13th level, you can use you Uncanny Dodge to make a Dexterity (Sleight of Hand) check to force an attack that would otherwise hit you to instead knock a larger foe prone. This also forces the to act as if the attack missed.

Size Advantage

You’ve become accustomed to your smaller frame and lesser weight, allowing you to attack quickly, hide in smaller areas, and do flips and jumps many larger foes couldn’t dream of doing. At 17th level, you get automatic advantage on Dexterity (Stealth) and Dexterity (Acrobatics) checks. You may also take 2 actions per turn. If under right circumstances to sneak attack, both attacks count as sneak attacks.