unfortunately the dnd 5e and pathfinder dynamic templates are implemented in a way that is highly optimized and not flexible. Basically it is using hardcoded arrays in the json file expected to be with the right type and position.
This is the opposite of the normal sheet that is very simple and general (basically a json with 4 fields, group number, group name, property number and property text).
I think the best next step it is for us to implement some general APIs, something in the middle that will allow more flexibility. This is a great suggestion, that we received also from one of our Patrons and it is in our to-do list. Thanks a lot for your great feedback! much appreciated it!