Pretty much what you want to do.
Gotta either build or buy a head/body mount.
You could dual strap a flatish piece of wood to you chest then put an L bracket out and mount the camera. Or wear a backpack backwards and create a holder/mounting area in it. Any bike helmet you feel like drilling some holes through and then just attach a tilting release plate. That would be like 40 bucks, or none if you have parts.
One of the simplest solutions would be to invest in a gopro and mount it to a helmet.
Simple shoots like choking someone can be straight forward with just putting hands in front of camera or an operator holding the camera next to your head to frame.
Shooting the scene footage first and them composting your hands later will most likely not give you the desired look. Probably would be more work than you want.
Um if you do the chest mount you can do some cool angles if, instead of attaching the the camera directly at chest level you can attach a pole or monopod and another strap at the top of the poll while angling down the camera.
If you are not sure you want to spend the money or time making these things just do a simple headband and tape(whatever) the lightest thing you have that shoots video (phone perhaps) and walk around as test footage. Buy a cheap used pocket cam if you want. In great light they are capable of producing good looking shots.
It really comes down to how much work do I want to do vs cost.