I suppose it might depend on your graphics settings, but "corpse stay", as it used to be called, is more like 30 seconds for me, and that's with just Medium settings on a 7970.
That said, if you're talking about the way it affects gameplay as many others have, I totally agree. This graphical mop up is often what makes stealth too easy. They could have at least compromised and had enemies notice a pool of blood and become alerted and go into hunt mode.
As to your question though, all Ubi games are heavily encrypted. They never support modding.