Make a design which will cover the following topics:
- What exactly is in bContext? (need to LOCK DOWN whether it's original or evaluated entities)
- How to efficiently and reliably (in terms of being robust against mistakes) access evaluated/original datablocks.
- How will interface and python API access original/evaluated data.
The goal is: make a design document which we can just follow and start porting operators to CoW without worrying how to do it.