With the way BPs can go off feed, you probably need them to have all that body. It's not uncommon for some to go off feed for up to 8 months.
If you want a python that's small but not heavy like a BP, try a woma or children's python. Womas are laid back, thinner bodied than most pythons (resemble bull snakes), but do get about twice as long according to a few care sheets. Children's pythons are only about 3 feet but also laid back. They don't seem to have much in the way of coloring or pattern though.