I really don't see the point of stealing loot here.

Every second you spend stealing is every second you spend not doing anything, which will quickly bless you scorn from everybody else in Stone Vigil. Even then, once you kill the mob they'll drop the loot. If you mean they can steal AND get dropped loot, the very idea is dripping with imbalance. FF tactics introduced Stats Steal, that could work. Allowing a certain class to be economically superior to everybody else encourages single-class play. it's horribly imbalanced to the point that unless you make it pointless or affects everybody else in the immediate area, it simply cannot be balanced

Stealth is another entirely pointless system in battle, and also horribly imbalanced. The choice of starting an engagement AND breaking the engagement should be the ability of both parties, not only one side. By granting visual invisibility, you effectively break 98% of skills in FFXIV, a game where you need to visually click on something to use a skill

"Well then just remove the body from the screen, but they still can click on the enemy list!" No, that won't work. Even if you are still targeting the thief, you lost immediate visual cues: their stance, their movement animations, everything.

In a game where nobody but the tank is supposed to have the enemy's attention, what purpose could stealth have?