I had raid night and my brain is a little fried.
As far as WHM stuff, I just don't really feel like having a couple extra buttons with a little more interconnectivity is asking for much, especially when AST makes so much more sense to be the healer who can intentionally have limited DPS buttons in favor of setup tools that disguise support as DPS. I'd rather Water be its own independent piece of the earth, wind, water CNJ trinity. Regardless of how it's implemented though, Water I-IV actually have animations in the game already and are used by enemies and CNJ NPCs as well as Y'shtola, and Water IV is essentially a large bubble explosion. Though I see that more as a single target spell early game that upgrades to AoE eventually before becoming something else. I also just really want something like Aerith's Tempest action in FFVIIR or anything Aerith-inspired really.
For SCH:
It's not dissimilar to the SCH build I've had in mind really. I personally would like to see Biolysis replaced with SMN's lost Bio III and restore Miasma III as well. SCH is the healer who feels like its identity is being overshadowed by other healers in other ways. It's healing doesn't visually stand out in anyway that feels different to WHM's healing, and its sci-fi tones are heavily overshadowed by SGE now. Redirecting SCH toward its ACN roots gives us as poison healer which I feel like would stand out very nicely. Having a third DoT as well to revive that feeling of HW having your core 3 DoTs would be a great treat, perhaps something like Pain or Rasp from past Final Fantasies to go with the poison theme, and adopting Fester would also be nice.
As for AST:
I really can't say right now. AST is a healer that I know clearly what direction I'd like to go in, and I've thought of many ideas that I think help accomplish this--essentially having GCD cards that you play in advance on your party members, and then use another GCD to activate your cards, all the while generating a passive resource that you can give to other players to do your damage for you basically--potency magic attacks that come from you that other players detonate. That said, I feel very confident about 1 thing with the AST rework slotted for 7.0: Whatever we get is going to eliminate the bulk of AST's single target buffing. I can't say that for certain of course, but constantly needing to cycle through single targeting is the thing that the general player hates the most about AST and what makes it so undesirable for so many people. I think it's a massive deal breaker that they will address in some fashion, but trying to rattle my brain around ways to eliminate single targeting while creating unique card buffs that take the place of your general DPSing and still make solo-content enjoyable has been a tough challenge. I've yet to settle on anything that I'm fully satisfied with.