How bout having some sort of kill team rules? If they are still used, ages since i've played.
Also to steal an idea from a
lotr scenario that was in a white dwarf many moons ago, why not have it so two people play out the battle inside the titan, fight for control of it for example, whoever wins gets to use it in the following epic battle or if not contolled then partly damaged? But the two players that are fighting the epic battle are not told of the outcome, that way it adds a bit more suspence as they dont know when the titan is going to show up, whos side it is going to be on and what sort of fighting condition its going to be in when it gets there.
Alternatively if it is destroyed in the kill tea,/space hulk mission, roll a dice at the end and the mumber that is shown is the turn that it spontaniously blows up during the epic battle, but again dont let those who are playing the epic battle know when its going to happen.
Hope that makes some sense