I really can't think of any other base defense utility that doesn't involve its representation on the geoscape.
I do, however, have an idea for a simple implementation that is pretty much automated. Just like the radar, the anti-air battery would have a range circle. If your interceptors engage any UFOs within this circle, the battery fires a single salvo which is assumed to occur just before your fighters reach the bogeys. This is instantly auto-calculated with a 0 - 100% chance of each UFO in the group suffering structural damage, critical damage or being destroyed (only escorts would be destroyable while the "capital ships" could only be damaged).
It's simple, automated and requires no player input beyond attempting to engage within the battery's range.
One thing I like about Alien Invasion is how base defenses and interceptors can work in tandem.