Firstly, the fortress looks great! I believe you shared that older drawing of he fortress and my first thought was that it was a bit mediocre compared to the rest of the map. This illustration definitely isn’t.

No I get that you don’t want to draw all the buildings, but the blank version also doesn’t really work. I think there’s two things you can do.

You could add a key and maybe some other drawings around the fortress. Perhaps a floor plan or some cartouche like pieces with text about the fortress. This way the map (I call it a map but it’s more an illustration I guess ) won’t feel so empty.

Otherwise I guess you indeed have to draw all the houses. It will be tedious but I believe the result will be amazing!

That’s my two cents! Hope it helps!