I always find that when building architecture documentation after the fact, you want to re-factor or at least re-engineer a lot of the code base to account for

I always find that when building architecture documentation after the fact, you want to re-factor or at least re-engineer a lot of the code base to account for areas where lines are crossed or decisions were made that might be performant and functional but lead to poor maintainability or opacity to all but the most involved project participants. It would be great to see this document evolve into a guideline rather than a "this is how most of the code works today" document.