Close up the hallways. Even if it's star wars or any other high tech sf, you would like to minimize the amount of wasted space.
I don't know how you plan to tile the maps, but if you're going with 2 exits along each lon side and 1 on each short side, it will be alot of corridors.
Have you thought about doing just the overlays and corridors separately so you can put them down as needed?
That means breaking up the main map into more overlays, so you're left with just room tiles and corridor tiles. I'd make just 9 square long corridors and 4way intersections with 1square sticking out... Or maybe do 3, 6 and 9 sq long corridors and some corner corridors for even more cusomizability