Here is the 2.1 patch with the 22 different rules. I haven't done any of the cleanup I intended but it's still fairly tidy I think (with changes inside pd guts > pd calculate new states > pd rules).
@Hugo-Legrand that sounds interesting, looking forward to seeing the patch.
I came across this, which looks like a neat idea, except that it would be even nicer to be able to store those shapes as well.