Im no scholar or anything but if i were to do this, i love the idea by the way. I would keep my decisions and thinking consistent through the entire piece. If it were a set such as the WTC I would be okay with altering my thinking for each P and F. Because there is no way Bach had the exact same thoughts and characters in his head when writing each one, so i would be okay with making them different. Just keep the same mindset going, write down everything you can about how you are thinking about what you are you adding to the text.
Id be interested to know your thoughts on pedaling, i know it is a bit frowned upon for bach, but if bach had a modern piano, he would have used the pedal. He wasnt closed minded, he was open to and embraced innovation. Or so my reading tells me.
Good luck with this!