Making a wooden knife is a good idea when trying to think out a design. Don't worry about the little details like the front of the scales or blade style, just rough out a handle with a tapered blade coming from it. Try and get the feel in the hand so it seems natural.
I like #3.
Now, as to a critique on the designs:
I'm not sure about the dip on the front of the scales at the ricasso. Maybe a smoother curve?
Not sure that the finger choil is going to work as it is drawn. Looks like the transition will chafe the fingers.
You might need to take the two small points off the scales at the lanyard hole. They might be problematic in shaping and finishing.