ok, I know it's late but still I have to write my opinion you know so:
I didn't have 6073 as a child, always wanted it. Almost done making it now. It is a smallest version of 6080 that came in the same year. It's got a unique dungoen. 6 BF minifigs. The only set with 6 BF shields. On 1984 was the only Black Knight, the only red and black plastic capes, the only black feathers for a while (and still not very common), the only set that had 2 arch 1x3 in red and 24 gray walls which is still a lot. The only castle that can open, but it's rear walls only rotate 90 degrees rather then 180. I'll take Jojo explanation for the red gate cause it's probably true.
I toyed once with the idea how the castle would look with a gate in another color and....
This is the result:
Well I guess it still look best as red
Final grade: 8.5/10 it could have been 9 or 9.5, I don't like the fact that the side of the castle is too nerrow, I guess another wall at each side could have made the difference.
P.S. to Jojo/Ben: I have a small mistake in the picture (didn't have the power to change it again), can you spot it?