To some extent it's there already. If you open an epub and one of its content html files, you can right-click in its code view area and choose 'Split at multiple locations'.
Unless something has changed recently, I don't know of a way to split every html file in the whole epub in one pass.
Or, I suppose, if you don't want to actually split the files but only want to force the reading device to do a page break, then using Regex to insert a set of dummy paragraphs
<p class="breakhere"></p>
plus something like
p.breakhere {page-break-before:always}
in the css file, should work across the whole epub.