I had a similar method to you! I basically argued that first it was because the GDR was economically redundant so they had no choice but to build a wall, then I argued back saying that wasn't the fault of the GDR but rather the tactics of the FRG via magnet theory, and the GDR was economically okay in relative standards. Then I argued that the political repression they inflicted on the citizens discouraged political conformism inducing the necessity of the wall, then brought it back again saying society was already inclined to hate communism even pre-1949/pre-GDR because of the wrath of the Red Army/Hitler's anti-communist propaganda, e.g. people had been fleeing westwards (mass exodus) before the GDR even existed
Everyone else I've spoken to focused the question around the niche - I don't think our vaguely similar methods are wrong but just a different interpretation of the question?
This exam was over a week ago and it's still stressing me out! Sigh