That`s usual in games like Warhammer & W40k RPG, where you have long-term injuries and as Annyliese said it´s from the Eberron setting. It´s also used in campaigns with the "Gritty rules" or "Dark ´Dungeons" variant ruleset.
The Prosthetic limbs are also artificers items, and since the artificer would not be in the EA at least, I do not think we would see it.
As an idea for an Artificer DLC that would be awesome. They would have to create a "permanent injuries" mechanic that does not seem to fit the kind of game Larian use to talk about in interviews but could be interesting to use it in high level difficulties or maybe an ironman/survival mode.
