I know there a lot of these already since WHM is so barebones right now. I'm going to be fairly ambitious with changes while trying to keep it feasible for developers to implement it(haha).
I'm not going to specify potency gains or increases or try to balance out the damage output. Just assume if this is implemented that potencies will be balanced out.
WHM REWORK:
-Cure upgrades into Cure II at 26 and the upgrade trait replaces Free Cure
-Regen gets moved down to level 30 instead of 35 just to smooth out those dungeons for WHM
-Lily System gets FULLY unlocked at level 30 upon changing to WHM. This includes the Blood Lily
-ALL GCD heals feed into the Blood Lily. Now only needs to heals to grow a Lily instead of 3. Potency=Stone/Glare x3 and gets a potency increase at the same levels as the main nuke. Can stack up to 2 Blood Lilies
-Afflatus Solace unlocks at level 30, Afflatus Rapture is the new capstone at level 50
-Cure II and Medica turn into Afflatus Solace and Rapture respectively when a Blue Lily is formed
-Medica II is lowered to level 46 to make room for the new capstone at 50. Potency increased at before the level 85 trait so that it's always stronger than Cure II for single target as well
-Cure III is removed. Medica/Rapture potency is buffed to its potency to compensate(if it's even necessary)
-Assize Cooldown is reduced to 30 seconds and has 2 charges
-Level 60 Capstone is now Flood and replaces Tetragramation. AOE DPS GCD with falloff that feeds the Blood Lily and increases own damage by 5 or 10% for 20 seconds. This is the start of a 60 second burst window cycle. Uses Yshtola's Water IV animation. Instant cast
-Prescence of Mind also gives 1 Blood Lily. Retains 120 sec CD. Larger burst window every 2 minutes
-Quake is another AOE DPS GCD with falloff that is a combo action after Flood. Also feeds the Blood Lily. Instant Cast. Replaces Asylum
-Tornado is basically Aero 3. DoT has a 15 second duration
-Divine Benison changed to 60 second CD. Upgrades to Aquaveil and gains both affects later on
-Plenary Indulgence becomes a 200 Potency AOE barrier. Activated immediately, you don't need to use a heal to activate.
-Holy/Holy III get a 1.5 sec cast time
-Thin Air only affects healing spells(including Raise)
-All heals have a 1.5 second cast time
This cements WHM design as a GCD focused healer and gives it a burst window that interacts with healing. The core of this whole design is Afflatus Misery. You want to set yourself up to use Misery as many times as you can during the 20 second Flood buff. Assize, Plenary Indulgence, Benediction, and Lilybell and there to cover healing during your burst. Regen is your most powerful tank sustain tool. Medica II is the most powerful AOE sustain tool. You will be using heals to fish for Misery outside of burst windows some.
Burst window goals would be to use Flood, Quake, 2 Tornadoes, Dia, 2 Assizes, and as many Miseries as you can fit in 20 seconds. This would be a whole 20 seconds without Glare or at most 1 or 2 Glares. You will also be using Glare considerably less often outside of this burst window as well.
This would likely cause over healing on the WHM part in a lot of fights to setup burst windows but that is more encounter design's fault.
I wanted to bring back the Conjurer roots but I would settle for more Holy magic if that is not a possibility.