@just_jeepin
As a last resort you could try this:
1) Convert epub to fb2 (with Calibre, for example)
2) Install AlReaderX (from
Google Play or
directly from their website). It has the feature to edit fb2 books, right from the place where you were reading it. The easiest way enter the editing mode is assign it to Quick Settings or some gestures/tap zones.
You might loose some formatting of the book in the process of converting epub -> fb2 -> epub, but if this suits your use case, why not?