Very well written article with some good advice. We found very early on the need for multiple AWS accounts and managing varying levels of access to all of them has been challenging.
I also recommend looking into using SAML with your own login provider, if you have one, to assume individual roles in AWS accounts.
Would you mind describing your needs? I read the article and I still don't fully understand the need for multiple accounts -- seems the article is more about the tool. I would understand the need when it comes to API rate limiting, but I have never ran across this on a million+ session/day website.
I also recommend looking into using SAML with your own login provider, if you have one, to assume individual roles in AWS accounts.