Well, I have a couple ideas...
Pros: you bring back spreading DOT (helps with dungeon packs), you play more into the SCH theme of 'set up mitigation' (it feels more thematic to deploy a shield rather than just Succor it onto people), SCH is made stronger, button has multiple use cases
Cons: It kills SGE. A SGE/SCH shield lasts 30s, so you'd be able to put it up at literally any time, and be guaranteed that it either covers a hit, or will be 'ready again' at the same time it falls off. But, an Adlo is 540p effective shielding, and a Succor is 320p. SGE, however, has to use Zoe as their 'Deploy Adlo' equivalent, and it's already 'not as strong', making their usually 320p shield into 480p. Zoe's 90s CD, so you'd have SCH being WAY better at mitigating big hits. To keep the playing field balanced, SGE would have to see Zoe lowered to 30s in order to not get told 'you are bad class' (you can see DSR and the Holos shield addition to see that SE thought that 'not as much mit as SCH' was a very real problem for SGE on release). BUT, Zoe doesn't just affect shields, it affects all healing spells. So now SGE's base healing has just been buffed through the roof to try and keep parity with SCH, and now it's an arms race situation
Giving it a second charge though (keeping it's 'recharge time' at 90s) would maybe work, and be less 'destructive' to SGE's health in the PF-Sphere
I do get a small amount of.. some feeling or another from this line, maybe schadenfreude or something similar. Because I do wonder for WHM, 'what healing plan?' Anything that happens to us, we respond 80% of the time with 'Rapture'. The 'healing plan' is something the other three healers do, rotating through their OGCDs, WHM just goes 'Magic Missile! Magic Missile!' with the same heal over and over until they have no Lilies left, at which point it's Cure 3 or Medica 2. I remember my 'healing plan' as a WHM in TEA. It was 'Temperance at 5 stacks, do 4 Medica's, use 3 Lilies with PI, spam Cure3 until phase is over'. Compared to my Noct AST partner who was doing some mad gigabrain stuff on their OGCDs, use Star here, pop it here, use CO on this stack count, use CU to cover point A to point B. WHM is just bruteforce healing power, and that can be useful in prog, fun in prog even. But once you don't NEED that power, it doesn't have much else to keep it feeling engaging.
The one time I felt clever on WHM in recent years (like the past 4 or so) was doing UCOB to help a friend's prog, and I had the idea to purposely hold Assize (at a damage loss), so I had one extra 'heal while moving' to cover Blackfire Trio's stack mark damage