Base Class: Rogue
You have mastered the art of capturing and subduing other creatures without drawing blood. Cattle rustlers, poachers, and bounty hunters all make a profession of this archetype.
Blind Spot
Starting at 3rd level, when you either grapple or climb onto a creature whom is eligible for your Sneak Attack feature, the creature becomes unable to see you until the grapple ends or until you are dislodged.
Unscrupulous Scrapper
When you choose this archetype at 3rd level, you gain proficiency in the Athletics skill if you don’t already have it. Your proficiency bonus is doubled for any ability check you make that uses either of those proficiencies.
Additionally, you can use your action to try to render a creature under the effect of your Blind Spot feature blind, deaf, restrained, or unable to speak. When you do so, make a second grapple or climb attempt against the creature. On a success, your target suffers the condition you choose until the start of your next turn or until you release it (whichever occurs first).
Take Hostage
At 9th level, when a creature that you are grappling grants you cover against an attack and that attack misses you, you can use your reaction to force them to reroll the attack against the creature that you are grappling.
Take the Reins
Starting at 9th level, you can use your action to exert limited control over a creature you are climbing. When you do so, make a second climb check against the creature. On a success, choose one of the following effects.
Forced Attack. You force the creature to make one melee weapon attack against a target of your choice, which may even be itself. If the creature has advantage on the attack roll it deals your Sneak Attack damage on hit.
Forced Movement. You force the creature to move up to its speed as you direct it, without provoking opportunity attacks. The creature can't move on its next turn after you do so, unless an effect (such as the Dash action) grants it extra movement on top of its speed.
Bushwhacker
Starting at 13th level, when you are hidden and you reveal yourself by disarming, grappling, shoving, or climbing onto a creature, you remain hidden until the end of the turn. If you end the turn in a new hiding place, you remain hidden until discovered.
Busy Hands
Starting at 17th level, you can use your Unscrupulous Scrapper and Take the Reins features as bonus actions, rather than actions.
Frankly, I can't fathom as to why I "published" this, think it was just on a whim, and I must have underestimated how visible this was. If I could delete it, I would. But since I don't seem to be able to, thank you for posting this. Just for clarity, I absolutely did just replicate your Kidnapper subclass with a few tweaks here and there, mostly just verbage for a lighter tone. So on the off chance anyone else sees this, go look at this guy's other subclasses and such, because they're pretty cool.
Hey man. I just wanted to say, this is an almost word-for-word copy of a Rogue subclass that I posted online, and which can be found here. I would appreciate if you at least gave credit to the original.