Phillip Khan-Panni is a successful competitive public speaker and corporate communication coach (who also specializes in advising business people in cross-cultural communication). He writes about his professional interests on several different blogs, most of them WordPress-based, and wanted to offer his readers a single unified feed they could subscribe to read all of his content.
I set this up for him using the RSS Multi Importer for WordPress, whose primary function is to generate content on your WordPress site aggregated together from multiple feeds that you can select, but which has an additional function of generating an RSS feed-of-feeds that you can publish from the WordPress site where you have installed the plugin.
Despite this latter function being described by the plugin’s author as “beta”, it worked well for me. Here is a Page aggregated from Phillip Khan-Panni’s online output and here is a link to the corresponding RSS feed.