I think the titans should also severely damage near by ships when destroyed as well, a fitting end for them.
Oh man, this. Just imagine the energy needed to operate one of these ships: it's got an incredible amount of mass (from the looks of it, it's heavier than an Argonev Starbase), and it manages to propel that mass at amazing speeds; it's almost as maneuverable as a capship!
Anything with that much power has just got to go boom in an amazing way. Maybe send out an explosion shockwave covering a very significant part of the gravity well (half or so), bypassing shields and dealing a big jolt to capships, and flat-out obliterating lesser entities like construction ships and light frigates? Enemy and friendly alike, of course.
The damage of such an explosion would have to be carefully balanced so that people don't throw a titan at an enemy just to clear their grav well with the explosion (titans aren't that expensive in the late game if you have a large empire). I'm thinking something like:
* Low-level, "Heavily Damaged" capships (per the voice announcer) would die in the explosion
*Construction Ships - gone
*Raloz - gone, except maybe with full hull upgrade research they may survive
*Cobalts - gone
*Corvettes - gone
*Fighters - gone
*Protevs - gone
*Weaker light cruisers such as Cielo and Hoshiko - probably gone, but maybe survive with hull point upgrades
*Kodiaks - can barely survive if at full health
*Capships with full hull - survive but takes about 25 - 40% of total hull points depending on level
*Titans - "mild" to "moderate" damage
*Starbases - "mild" to "moderate" damage to a fully upgraded SB; very heavy damage to one without any hull upgrades
*Planets - if they get hit by the shockwave, it's like ~5 volleys of bombs hitting it all at once (about 400 - 500 damage to infrastructure / planet health)
*Modules - heavy (40 - 70%) damage, but most modules except mineral extractors should survive due to their high armor
Also, the shockwave damage should taper off slowly with distance -- not to the point that it barely tickles a fighter's nose at the edges, but something like 20% less damage at the outermost reaches of the shockwave compared to being right on top of the titan when it explodes. It'd still obliterate fighters even at the edges of the shockwave.