Changing name of leaf file in Page Bundle

Hugo Page Bundles are an especially useful feature that allow keeping related items of a page all together in the same folder. That said, the one issue I’ve seen with a larger project is that it’s harder to identify the files (all “index.md”), especially in an editor that displays just the file name in the tab.

Moving to Page Bundles, you might go from something like:

TopicA.md
TopicB.md
TopicC.md

to:

TopicA/index.md
TopicB/index.md
TopicC/index.md

Is there a way to change the leaf file name from index.md to something more expressive, and still have them build to index.html?