What's REALLY nice about this boat is that she's SO PRETTY!
When one's lust is well nourished, the problems are much less problematical, and the rewards are greater. Think of the effort required to restore a Ford Siesta or a Jaguar: same work, same hours. When you're done with the Siesta, you have a Siesta. But, when you're done with the Jaguar, you have a Jaguar!
Now then, about that transom cut-out: Most of our boats have doors cut through the upper sides of the hull. Mine appears to me to have been cut out after the hull and deck were joined. Other very similar-looking boats have their doors in different places. Suggests to me that my supposition is correct. Structurally, that cut-out transom is really just a big door (presuming enough of the corners are intact enough to keep the sides in place, and it looks as though it might be OK). As for safety, consider that most of us have open scuppers, most of us have boats that don't make the slightest pretense about being ocean-going (no dogged doors, watertight hatches, small gasketed ports, freeing ports, etc.)
You love that boat as she is in your minds' eye? You a sucker for hard work and the inevitable punishment? Buy the boat.