What it says on the tin.
SMN is considered "brain-dead" or "lobotomized", but is still a DPS Job with a DPS rotation. A rotation which largely consists of using 3 buttons, Ruin 3 (more that Ruin 3 turns into Bahamut/Phoenix attacks during DWT/FBT), Gemshine (which is spammed in various ways when Summons are out), and Astral Flow (which is more situationally used when Summons are out)
That's the rotation itself. (There's technically also Energy Drain, 2x Festers, and a Ruin 4 per minute, and Enkindle once per major Summon, but let's set those aside for now). If we took that base and gave it a bit more of a healing flair, it would still be largely approachable to people and give them a few more buttons to press.
Even treating the combined buttons as one (e.g. Ruin 3, Astral Impulse, and Fountain of Fire as one button), you have things like ~50 "Ruin 3" casts, ~70 Topaz/Ruby/Emerald Rites, and ~50 Crimson Strike/Crimson Cyclone/Slipstream/Mountain Buster casts. Or therabouts (using P5S data). Basically, "If Dia/Bio/Combust/EuDosis were a regular part of the rotation and we had a third button that also split the load."
As opposed to the "180 Glare cast" "rotations" people have linked before.
If something like SGE had a rotation like that, allowing Kardia healing with a bit of an interesting rotation and sprinking of oGCDs, would this be acceptable, or are people wanting a rotation more like NIN?
EDIT:
Note that this wouldn't actually require adding anything, it would just require changing up how the existing buttons are used. SGE already has roughly four attack buttons that get use in single target fights - Dosis, EuDosis, Plegma, and Toxicon. Having some kind of a system like SMN that had you rotate through using them in various ways wouldn't necessarily even require additional buttons be added to the Job, just repurposing the existing ones.