The model is great but didn't they watch the Wrath of Kahn? Ok, Star Blazers was 70's era so I guess it predates it
Space is three dimensional while oceans are two dimensional. Oceangoing battleships have all the guns on the top. In space there is no top so you need guns all around. You just have to sneak up underneath this thing.
That's what I don't really like about the Star Trek and Star Wars ships. Most of them have a definite top despite never having to land.
Now the Death Star, that was a classic space opera battle station. They were always either spherical or teardrop shaped. It's OK to have a back, that's where the engines are.