If you ever visit the healer forums, I pitch this argument all the time. I call it the "4 Healers Model", which in a nutshell is "We have 4 healer Jobs, so why not make them play differently so they can appeal to different types? Leave one as it is, change 3 to variations so that people who want more complexity have options?" The typical way I pitch this is "Leave WHM as it is today, give SCH its SB damage kit back, give AST it's SB/HW Cards and extra effects (Time Dilation, etc) back and more party buffs to make it a buffer support, and give SGE a Caster-esque rotation like SMN or RDM have where Kardia procs for more and their gameplay is about efficiently using Kardia while properly performing its damage rotation. This way, every type of player would have a healer Job they can main and enjoy."
I get called LOTS of names in there and am the subject of near constant dogpiles - to the point the common Healer forum posters will dogpile on me in any other part of the forum now, such as General or the Tank or DPS forums - since they don't like the idea of a compromise that has even one healer Job still appealing to people that like healing as it is today.
They're inflexible and uncompromising and don't realize it, but I genuinely think that would be the best solution. And yeah, I use both Caster and Ranged and Tanks as examples - SMN vs RDM vs BLM, DNC vs BRD vs MCH, WAR vs PLD vs DRK vs GNB. They insist that ALL healers must be more complex or no deal. And when I point out "no deal" means the status quo and we stay with what we have now, they go ballistic.
They also like insisting that their complexity won't affect people that don't like complexity...but we all know that isn't true, as you said well here:
In short - I agree with you. Why not? Why not have a healer Job (or even two or three) that add complexity for those players that want it? As long as at least one is still enjoyable to the people that like current healing, this shouldn't' be a problem and everyone wins. (Except the people that want ALL healers to be more complex and won't be satisfied until people that don't like complex DPS on a HEALER class are out in the cold.)