Idea #1:
It would be nice if instead of using touch to draw, a swiping touch gesture would be used to move between pages.
Also, if you could navigate through pages as if they were a notebook, with one page on top of another.
Since I am a developer myself, I know this might be hard: if swiping on the page could "peel back" the paper to reveal or cover the page underneath.
I drew this idea in Xournal and attached it below.
Frankly, I find pushing the next/previous page buttons a bit hard.
A Delete Page button would also come in handy.
Idea #2:
Sometimes, I find myself squeezing in text at the bottom of a page. I was thinking about an "Infinite sheet of paper" option that allowed note writing to continue on and on without boundaries, either just downwards or in all directions.
Concept drawing of Xournal page turn