'So, in order that everyone is able to do as they wish with their backplots, I can't?'

The only thing that stops you doing whatever you want with your back plots is you. If you can't have a backplot without someone elses map to begin it in, someone else storys to base it on, if you can't find a place in the avialable creative possibilities to carve a niche, with out carving up other peoples or carving out from theres, perhaps you need to rethink your approach.

'There is nothing in his backplot that any other priest has to have followed.'

And there wouldn't have been the impression there was if you had written it in different ways.