What if Rift Herald gave the distortion enchantment temporarily?
Remember Distortion from before they removed boot enchantments? The stats were:
Distortion: Reduces cooldown of
Flash,
Ghost, and
Teleport by 15% and grants each spell an additional effect:
Flash: Gain 20% movement speed for 1 second after use
Ghost: movement speed bonus increased to 40% from 28%
Teleport: Gain 30% movement speed for 3 seconds after use
Such a buff would be perfect for the Rift Herald since the Flash/Teleport and Flash/Ghost are most commonly used by top and mid laners, but not junglers, ADCs, or supports. It allows Top laners to have more global influence by reducing the cooldown of their TP/Ghost but it's lesser value to ADCs/supports and providing a more selfish reward overall means it doesn't just make top and adc/support switch lanes. Of Course the Ghost puff will be a little different thanks to ghost changing a bit since Distortion was removed, but it still seems like a pretty good idea to me.