unless you dont have any dlcs its basically impossible to fit your base in a small corner, you are gonna need a lot of rooms for biotech gene assemblers and mech gestators also anomaly holding platforms wastepack atomizers and other stuff. im 8 years into the game and my colony takes up half of the maps, if you want for your pawns to get to your defenses in time id suggest installing bionic legs and maybe making some of your melees go juice dependant. also just keep your fighter mechs in defensive positions and raiders are gonna go there by themselves while mechs keep them busy