I would like such a thing for perimeter defense because i dont like to always watch out for my defenses, cos normal spacestations cant eliminate a little bit more serious attacks... So u have to set up starships to defend your important borders, but if you make them hold position, they are very ineffective, if you let them move, you'll never see them anymore... Or if you set them on patrol they're sort of ineffective again, except the long range ones (described in another topic)...
A battle station would be nice cos i dont think its really fair that 2-3 stronger ships can turn a huge station to spacedust. Battle station should have massive shieldings (as it has got plenty of space for both shield generators and an enormous reactor core) and long+ range weapons.
It wont be a problem if it costs millions of dilithium and tritanium, a player is not an AI, cant concentrate on many things at the same time, specially cos of the screen size and type of controls the games nowadays have. Its not a good thing to care for your defenses (probably at more than one fronts) at every encounter, especially if you have to start a research, comission ships, control your attacking fleet, etc. Players would, and will collect the raw materials for such a starbase, cos it will worth it...
Remember the old Ferengi guys?? "Time is money, frends!"

But as long as we dont have such a thing i'll describe here the best way of setting up a defense, i have found this far:
Build 2 space stations, but leave a small place between them, watch out at the height where you build them. At zero (normal) height they are fine, or maybe a little bit higher (upwards). [height i mean, hold shift while setting your station's location, higher is green line, lower is red line near cursor] If you have these 2 stations ready, place a sensor station between them, but as low as you can! (hold shift, drag down). Then build a lot of excelsior refits, or any ship you would like, but they should have long+ range! Select your ships and with the defend command, set them on the sensor station. They will start to orbit around it , but they wont get stuck in the space stations because they're moving beneath them.
Works with little losses and good damage output (against hard AI).

The reason the mod doesn't have any powerful defenses is because it promotes turtling, which many people view as being a noob strategy and hurting gameplay online.  I personally prefer the more dynamic strategy of actually attacking.