Since most people use Google Reader as the RSS reader anyway. The deails would need to be worked out, such as should downloading mark the items as read?
Put an option on the home page that converts downloaded content to PDF instead of HTML since PDF is faster on most screen readers.
Put a checkbox on the main screen that grants the ability to convert downloaded images to grayscale. Since most ebook readers are greyscale anyway, and image size hurts performance, this will help...