I remember playing this game a long time ago - I think at least four, five years back or so. I just recently found it again. I really like how it's grown!
Now, personally, I like Titans, and they don't seem to be getting as much units as the others, so I have two ideas:
A lightly armored, low mobility unit with really high vision and an attack range of four hexes, along with high damage. It's not built for offense very well, except maybe for support, but is meant for defense - it can be positioned as a guard to shoot at enemies before they get close, and to see them coming. It could also be used in traps that utilize the fog of war.
A burrowing unit of some sort - perhaps instead of Bury, it would be called Light Refraction or something like that? - with high vision, high mobility, but no attack and low defense. They are meant to utilize the Titans' Teleport ability. They could move near the enemy bases while camouflaged, allowing Titans to teleport in for quick surprise attacks. Maybe they could also somehow have lower health?