Hi, Michi - congrats!

Not sure about your future plans, but there's a huge need for good collaborative writing/editing programs for traditional book publishing. Collaboration with developmental editors, copyeditors, agents, publishing staff, etc is both essential and extremely painful.

From the looks of it, the structure and output needs for book projects are less demanding than what you've already implemented, so it might be a worthwhile adjacency to explore.

Hope this helps.