Ruthless end-to-end testing helps. Really hard on the short term, pays back on the long term. The suite is the specification.
The tests tell you what it's supposed to do, not how it does it.
Note that requirements change, and bad tests will break on no requirements. Telling the difference is an exercise for the reader.
1. Ask for forgiveness and do whatever you think is prudent regardless of org structure.
2. Find a better org structure elsewhere :)