Further to #587096: Work with custom body_field inside a fieldset and #967158: Support body field of "project-issue" type, can I suggest that your notes on using the Better Formats module make a brief but clear reference to the fact that Better Formats requires the node editing form to have the 'format' selector inside 'body_field' alongside the 'body' textarea. This is standard for Drupal core, but custom modules are allowed to restructure this any way they like. Whilst it is non-standard, it is not impossible nor (as far as I can tell) discouraged to do this, so a module coder could be forgiven for doing so - and for not realising that this is why Better Formats doesn't work! A quick note explaining the requirement for compatibility with BF would have saved me hours and hours of tinkering.

Now that we finally have it working, I'm delighted - it's a great piece of work; thanks for doing it!