Accomodate Aerial Enemies Better in the Randomizer

[1SDANi]

Aerial enemies should only be able to be replaced by Aerial enemies. There are numerous cases throughout the game where enemy spawns may just end up with a ground based enemy falling into the abyss.
Average vertical displacement between enemy types. The entire challenge of fighting Monsoons is that they're generally so high, but when they spawn to replace a ground based enemy their height is not changed to accommodate. Each enemy type should have an "average displacement", the difference of which is applied when replacing enemies to adequately approximate their intended combat design.