well, a lot of the Ailments that were suggested, I don't see being added any time soon. As for cross class gear, that suits 1 talent type is unheard of, so its unique in that regard.
However, we do have a cleric, and a Harmonic Saint, from what I gathered, your suggestion is more 'realistic' treatment of wounds and Ailments while also dishing it out as debuffs. This doesn't go well with the 'fantasy' idea of the game, now again its a good idea, but it lacks kindof a fantasy vibe. If it backpacked off of Cleric, like if Cleric was upgraded to Triage Cleric or Field Medic even Holy Cleric as you basically become a Harmonic Saint later, and had its own specific types of weapons/gear I can see this working, and seeing how Cleric is underpowered by a large degree unless you are a Saint or have insane healing gear, or both, it can use some love, maybe with some elements from this suggestion. Cleric also lacks progression so again elements here can be added in, like does one go into the realistic healing or the use of magic? They can probably whip up a story behind this too, that involves the church in some degree, and the field of science (as these were issues in our own past history where the church would attack people for studying the human body).
In a way we do kind of see a resemblance of this in G22? Where you have to in a way, become a Triage medic, but very briefly to counteract a illness (trying to not spoil the story). Also most healers in the game have medical equipment around them, herbs, and beds, so to add onto that, it is possible, but we never delve into it nor touched upon it in the game.