Firstly, let me state that I am not a certifying engineer on the DC-10, or any other aircraft. Which, I assume, precludes me from speaking from a manufacturer's bias.
While the DC-10 engine pylon may not be designed to separate inflight, the result, if it did, would be the same. It would go up and over the wing. Damage to the wing is unavoidable. In order to make the pylon/engine assembly fall down and away, all that is needed is to make the front pylon mount weaker than the aft. The aft mount is somewhat higher than the line of the thrust vector, as you call it. If the front mount lets go, the engine should pivot somewhat downwards. The thrust vector is now down for good. If the rear mount holds, then the wing is saved. If it lets go from the extra stress imparted to it by the torquing motion and from its own weight, then the assembly will fall down and away from the aircraft. It will not re-vector itself, go forward, up, and then over the wing. Impossible. It was my understanding, from an ariticle I read several years ago about the L-1011, that this is what Lockheed had designed. If it was only theory, then they let a good idea go to waste. In which case, it was very good that they made sure that none of their RR engines ever fell off.
As far as the THY crash is concerned, McDonnell Douglas knew of the deadly potential of the latch problem from the AA Windsor incident. That aircraft was spared the same fate because it was nearly empty at the back. Without the extra load, the floor held. Unfortunately, the THY flight was full to capacity. After the Windsor incident, McDonnell Douglas got the California senator to pressure the FAA into not issuing an Air Worthiness Directive. They were successful. Until the THY disaster. It was only then that the FAA stood firm and grounded all US registered DC-10s. McDonnell Douglas knew of the deadly potential of the problem. But instead of addressing the danger with a technical solution, they instead addressed it with a political one. That McDonnell Douglas made a bad design, is not unforgiveable. What is unforgiveale is what they did after they knew. Should they have had the foresight to put the hydraulic lines through the roof, as did their competitor? Well, if they had done destructive load testing, they probably would have. Or they would have made a better latch. Or the would have fixed the problem right away. Or they would have encouraged an AD instead of fighting against it.
As far as the UA 232 flight, putting a third engine through the tail as McDonnell Douglas chose to do, did not take into account the possibility of an uncontained fan disk separation. But those things do happen. Unfortunately for UA 232, this N#2 engine location exposed the tail to engine debris from all angles and directions. In the Lockheed design, the N#2 engine is several meters away from the tail and the vital items it contains. While it is true that shrapnel flies out in all directions, the McDonnell Douglas tail takes the hit from all directions. It was gutted out from within. The L-1011 tail would take debris from below only, if at all. Every spinning engine is a potential bomb. So putting a bomb right inside the tail was perhaps not a wise choice for locating the third engine, even at the time.
But then again, McDonnell Douglas never foresaw that a N#2 engine would explode, taking out the tail control surfaces. Just as they never foresaw a rear cargo door giving way and sucking the floor boards and the oil lines out into the abyss. Just as they never foresaw an engine pylon mount weakened from maintenance abuse, either.
But that is what this debate centers on. The contention that it is not reasonable to have expected McDonnell Douglas to have foreseen such events, and therefore, neither they, nor their product, can bear any fault. Conversely, there is the contention that there were those who foresaw such possibilites. They worked at both companies. But as is Lockeed's reputation, they were always planning one step ahead. Costs be damned. But they paid for this with lower sales and the inevitable demise of their L-1011. McDonnell Douglas on the otherhand, met only the requirements and challenges of the day. Nothing more.
Does this mean the DC-10 was an unsafe plane. Of course not. As I said earlier, I have flown on it in the past and do not fear it. But it is a lot safer now than it was 30 years ago, and many things about it rubbed some people, even technical people, the wrong way. And that is what the original poster was asking when he started this thread. You know all this stuff better than me, so I don't hope to educate you.