Gorgeous color! Now that I've been breeding for about 10 months for food I am starting to play around with certain animals as hold backs. Right now I'm selecting for long hair and trying to make a rat with out the dark stripe down the white back but still with the dark head. No idea what it is called.
Sounds like you are aiming for bareback or capped? Bareback has the colored head down to the shoulders, while on capped the color is restricted to just the head.
Why keep a snake? Why keep any animal? Because you enjoy the animal, find something beautiful and fascinating about it, and it fits seamlessly into your lifestyle.