If you're down with Django and python that's my preferred approach (I have hateful memories of PHP) but hey, I'm open to anything. I toyed around with it just a bit today and it seems very possible.
Just to be clear. Sage/Stras what are your goals? It sounds like there are multiple things going on and I just want to get my head around them and understand where I may be able to add any assistance. (my day job is helping run a relatively large video game studio, but in the olden days I used to do a ton of more technically oriented content work, so I am more than willing to get my hands very dirty)
1. It sounds like stras is interested in making an online character sheet that is user editable and allows for custom extensions (user definable moves for example)
2. Sage are you looking at publishing the whole text as HTML and then possibly outputting as pdf from there?
3. I am interested in different ways of displaying and presenting the book data. For instance I think my campaign would benefit from class packages/character sheets the encompassed both the characters and the rules similar to world of dungeons, but of course bigger.
Sage it also sounds like you would like to focus and solutions around Python and Django?
Sorry for being simple, I just want to make sure I understand where folks are and where the community may be able to focus and help.