I agree with you, Shermae, on the Bahrain defs. SG comes close but there are so many degrees of each variation for the reasons you mention.
Now Saudi Arabia - airplane, gas/oil plant and dam defs - there's a challenge!
Two printers, several series with King Saud and Faisal cartouches, three watermark varieties that are difficult to detect and up to around 30 different values and colour combinations in some sets! Deep pockets needed for some values, too.
Just to give an idea, I mainly scan individual stamps but these came to me from an auction so these show a few of the variations of "dam" and gas/oil plant" defs:

