Remain a huge fan of the concept but self admittedly we've struggled to design ideas that we think genuinely work - with continued room to expand into several more alignment sets.
It's one thing for us to design 2 or 3, but realistically this system benefits by getting to 7 or 8 as in the image.
The question is how do you get the balance right and create meaningful different use cases for the sets? Does it become tedious as just another thing to switch based on your activity?
Skilling prayers are a popular idea but how do we do it so it's not just a case of now bring prayer potions (and potentially max prayer bonus) to every skilling activity with just another thing to manage.
I don't think we're closed off to ever contemplating this again but for the forseeable we aren't revisiting this, though perhaps someone will have an S tier suggestion of genuinely balanced and well thought out ideas. There's lots of awesome ideas amongst the suggestions but in practice we've not made em work.
For now I think it's more likely we move forward with filling out higher prayer levels with new additions to the current prayer book.