My idea, reduce the cost of Ultralisk to 100 min, 75 gas
Also, allow for overseer to infest enemy static defenses to incorporate that technology into Ultralisk DNA (Don't worry, will require upgrade to do so)
Example: Infest Missile Turrets will allow for each upgraded Ultralisk to be outfitted with missile turrets on lining it's spinal cord. These missile turrets can be used for AA attack and possibly in some sort of jet-pack capacity allowing them to fly. This makes them viable vs air in the late game especially in ZvP which gets dominated by Skytoss.
This may finally appease the Zerg masses and play an interesting role in the metagame.