Happy Ghast Altitude-Based Movement

This may be a bit technical, but I would like Happy Ghast to behave differently depending on its altitude while you're riding it.

At water level, its horizontal movement (X and Z axes) should be at normal speed (×1), while its upward movement should be at ×3 speed. As the Happy Ghast gains altitude, these speeds would gradually change. At maximum height, its horizontal speed would become ×3, while its vertical speed would return to ×1.

This would make the Happy Ghast much more useful both for building at high elevations and for traveling long distances. It also fits its balloon-like appearance and the idea that its natural habitat is high in the sky.