Deliberate mistake: It's surely an intended joke, but that the toilet not only survived the explosion but also the landing in one piece is very unrealistic. (00:57:15)
Deliberate mistake: The way diplomatic immunity is depicted in the movie is extremely inaccurate. While technically a sufficiently ranking diplomat could perform the acts shown in the movie without being subject to arrest, their home government would be requested to turn the diplomats over for trial, or the diplomat would be declared persona non grata and expelled from the country. A drug smuggling ring and murdering multiple policemen is far, far more serious than actual crimes that diplomats have been expelled (or handed over for trial) for in the real world. Additionally, the consul general and his officers would not be considered diplomats. They would only have limited consular immunity with regards to "official acts" in the course of consular business.
Answer: This scene is already in the movie (maybe only the Director's Cut). Riggs surfaces just off the pier, picks up a chain, strangles one man with it and breaks the other man's neck. The scene is cut considerably for play on television and in all versions of the movie in the UK prior to the 2010 UK blu-ray release (including the Directors Cut) - although some TV airings since 2000 have used the full uncut version.