There's no current way to control the movement of entities in any form, besides latching into NMS (see https://github.com/Morphan1/Denizen/blob/master/src/main/java/net/aufdemrand/denizen/utilities/entity/EntityMovement.java#L95-L115 ). But this does prove that it's possible, and it would be great if Spigot could add some cool API methods to do it.

This API should also include some form of EntityStartNavigationEvent, EntityStopNavigationEvent, and EntityCancelNavigationEvent (or just throw them all under one and call it EntityNavigationEvent) to track entity movement, allowing plugins to stop entities from moving into areas, make them never stop moving, or ignore anything that could cancel their navigation route.