Factcheck my Halfling Warlock Creature Cannon?

So, as the title says, the plan is to have a halfling warlock with the eldritch invocations Lance of Lethargy and Repelling Blast. As a halfling, the Nimble feature lets you move into the space of any creature that is larger than you.

Therefore, you could have an awesome action hero halfling slide inbetween someone's legs, point upwards, and at level 2 blast someone 10 feet upwards with repelling blast, reduce their movement speed to 20 (10 once they stand up), and have them fall 10 feet, landing prone, and taking an extra d6 damage. At level 12, this would deal an extra 3d6 damage, knock an enemy prone, and potentially reduce their movement speed to zero, meaning it skips their turn with a cantrip.

I personally would run this warlock as a hexblade with agonizing blast, meaning that you would get each eldritch blast to do 1d10+9 damage at level 12.

Is this build as funny as I think it is? Does the math math? If I'm wrong, let me know and please tell me how you'd make it work better/funnier!