Well you know, I made a draft for a Gigas/Icanus duel, that would make it much more sane and much more involved for the player.
It would start off with two Apothess destroyers at long range, sniping the reactor subsystems of the Gigas. Shivan carriers launch fighters and bombers to try and kill the Apothess destroyers. When the Gigas' reactors are destroyed, the Gigas would 'not be able to fire its main subspace weapon'. Then, when the reactor subsystems are down, the EA launch a large attack on the Gigas so the player has time to destroy the main URed cannons of the Gigas. When these are down, the Icanus warps in at medium range and begins firing upon the Gigas. Enemy Juggernauts/Destroyers will warp in to destroy the Icanus, as well as heavy Durja bombers attempt to destroy the main gun of the Icanus. When the Gigas is near 20% health, the Icanus has an overheat in its main reactor or something, then the Shivans launch a huge attack on the Icanus. When the Icanus gets back online, the Icanus fires once more and kills the Gigas.