I like it.
I am not sure if you are looking for suggestions or just showing what it will be, but if I was to change anything, it would be what the cap is made out of. I would use steel and square off the top edge where your lanyard is so the cap could be used as an emergency striker.
The other thing I would do is cut a groove around the body so you could dummy cord the cap to the body with some braided twine without compromising the waterproof body. You will still be able to remove the cap from the body to use as a striker if needed. It will also make it much more difficult for the cap to actually completely unscrew over time if you keep the dummy cord short enough. Kind of like a plastic G.I. canteen cap.
You are only adding one step in the manufacturing of the handle, and that is cutting a groove while it is on the lathe.
Then it really is a self contained fire kit. I like others hate using my knife as a striker.