Just a simple way to do stealth in a proper way, it can start at let's say 70% and gets improved to 30% by talents/items. And can work the following way, if you're stationary it becomes harder to be spotted as you blend in, but as you begin to move the outline can be seen if you focus your vision on it.
You can obviously expand on the idea, this is just a quick input by me. Best of luck!
50%

40%

35%

20%