Wait-wait-wait; How big are giant ostrich eggs exactly? Ostrich eggs are pretty damn big enough a kobold could -almost- fit in one if it were proficient with yoga, and giant ostriches are 9.53 times the size of normal ostriches. If their eggs scale directly in both volume and thickness of tissue layers, like the shell, we could drill holes in them, empty them out, and use them like little high-altitude kobold drop pods complete with shock absorbing seats and harnesses, a kick-open hatch, and a safe slot for weapons, and deploy CoraiUnki's elite melee troops in massive wrecking balls that roll down into a siege, crushing a few before revealing their contents. Or just stuff a fully armed dwarf in them without the aforementioned amenities and maybe they'd be a little more horribly shaken up and cramped, but bursting out of the shell in a very dramatic fashion.
Dwarven drop pods, in giant ostrich eggs.
Or we launch their eggs into a siege haphazardly after drilling many holes in them and filling them with leather pouches of corrosive chemicals and some glass fragments to bust the leather. Or explosives. They'd make rather nice mass-produced projectiles I'd imagine. Already spherical enough to proclaim them accurate, with a hollow center we can drain of fluids and replace with anything. Virtually no actual labor going into producing the projectile itself.