Aren't displaced thresholds there due to obstacles in the approach path, not because of runway weight restrictions?
Also, I seem to recall that the Singapore B777 engine fire was ignited after reverse thrust was used on the engine in question. Things are often not clear cut & a 'one size fits all' approach can often lead to problems. That being said, often with an engine fire it is better to use reverse on the engine with the fire if it is still operating. Just get the thing stopped & the people out. If it makes the fire worse it may not matter - the people are getting out of the thing.
But what ever you do, there will the 20/20 hindsight brigade there to critique your performance, from the safety of their armchair. It won't all be bad - there will be some robust discussion that most will learn from. But there will always be some who can't get out of the way of their ego long enough to to think logically & rationally & consider other points of view. Those you just have to do your best to ignore.