Recommendations for highly selective colleges may vary, and are ALWAYS more stringent than the minimums above. Here are those for the US Naval Academy: English - 4 credits (including American and English Literature); Math - 4 credits (including pre-calculus, if possible); 2 credits (one must be a chemistry lab, and one must be physics); Foreign Language - 2 credits; History: 2 credits, including US and European History; IT - 1 credit.
No, you can't really provide a COMPLETE college preparatory education with just Boy Scout badges. You'll need to add higher level Math, a chemistry lab, and Latin (okay, so Latin isn't required -- it's definitely needed, though!). You can, however, provide the foundation for an excellent education using the Merit Badges as a starting point. Although the "No more, no less" rule applies to the badges, that doesn't mean that as a parent, you cannot require MORE to meet homeschooling requirements. Because they've done what's needed for the badge does NOT mean that you need to be finished with the topic.