Would a surgery for large-scale removal of adipose tissue in obese individuals ever be viable, or even theoretically possible?

Lipoma : Yes it's possible- depending on symptoms or functional impairment. It's also smart to achieve tissue to ensure its not anything worse than a simple lipoma. See a plastic surgeon for details.

Fat removal: Not likely. Your fat contains receptors for a number of hormones and chemical signals. It would be unwise to remove those from your body. Also, it would not remove the fat from the organs in the abdominal cavity (like the liver for instance). So no, i don't see that becoming a cure for obesity. It would be purely cosmetic.