Make it possible to make some changes to the layout, like:
Image on the left or right.
Large card-style centered image with the headline either above or below the image.
Large card-style centered image with the headline on top of the image. Add shadow around white text to remain readable.
Change padding around images. Let the user choose vertical and horizontal padding. Make it possible for content to reach the sides of the screen (0 horizontal padding) and completely eliminate the space between articles (0 vertical padding).
Two or more columns of articles. Particularly useful for landscape mode.
Hide/show the favorites "star".
Hide/show the source.
Customize source name shown for every feed.
Disable/enable swipe left/right on article. The feature mark a read can be implemented with a longpress.
Make it possible to remove the bottom bar (not just hide on scroll, but actually remove).
Make it possible to make some changes to the layout, like: