I've posted this a bunch of times, but for WHM an intermediate lily step that allows existing moves to be upgraded via a new oGCD would nearly be good enough alongside a useful version of Fluid Aura. It expands the current optimization theory that healing lilies do, but could be applied to damaging spells. Get a 2nd DoT back via upgraded Aero/Dia to (Holy) Tornado, mini misery with upgrade Stone/Glare to (Holy) Quake, redesigned Fluid Aura upgraded to Flood, etc.

Is still easy to introduce players to, can be delayed for needed healing w/o DPS loss because of how long it takes to overcap lilies, can provide additional healing to be palatable to different play styles, can keep WHM tied to the GCD design-wise (most of the upgraded spells/abilities would be GCD based), builds off WHM's added system, and can bridge WHM's old semi-druidic and new holy light priest aesthetics.