The other straightforward answer to your question would be to have your sole beneficiary for your IRAs be a spouse who is more than ten years younger than you. This allows you to move from a Single Life Expectancy to a Joint and Last Survivor Expectancy which results in a smaller RMD amount. How small depends on the age of your spouse.
While this option probably isn't realistic for most people, I would pose a question back to you: What is truly important to you about reducing your RMD amount?
Like Jeff mentioned in his response, I'd recommend that you sit down with an advisor, accountant, and/or estate planning attorney and figure out what your goals are, and then come up with a strategy based on those goals. For instance, strong charitable intent would lead to a different strategy than leaving money to family members.
The other thing I would mention is that it sounds like that you aren't enamored with doing Roth conversions. If you were my client, I'd take a closer look at this strategy as you have some room available in the 15% tax bracket and it appears plenty of non-qualified assets to pay the tax bill. The specific strategy I'd want to look at is delaying when you take Social Security and then 'filling up' your 15% tax bracket with Roth conversions so you will have lower RMDs as well as greater Social Security payments.