I see this sort of feature as pretty low priority. Larian still has much to do with building out races and classes and balancing what is already there. I can only see emersion stuff like this being prioritized after the game is in a more complete state. Bodies disappearing with items left behind is my best hope for something being implemented soon.
It's probably more of a performance issue than an immersion issue in the end. Every instance of a body and blood is something the game has to remember. Now how big a factor that is depends a lot on the engine, and I don't know enough about that to say it's going to have a big impact, but we can say for sure that it is going to add up.
