Is there any real possible way that this won't change established character things for either the Eighth or the Ninth Doctors, and not annoy us, too?
There's nothing established, though.
The last time we see the eighth Doctor the Time War hasn't happened yet. The first time we see the ninth Doctor, the Time War is over and the Doctor is in clean-up and PTSD mode. What happens in between? Could be anything, really.
Hurt happens to fall in a hole that hasn't even been sketched out beyond throwaway references. Fans assume certain things must have happened and to whom them happened, but those are ultimately only fan assumptions.
And, frankly, Doctor Who
has been a series that has always played fast and loose with its own past. Moffat grew up at a time when "The Deadly Assassin" was considered by some fans to be an atrocity because it ran contrary to what "The War Games" revealed. If Moffat wants to do something as radical with Hurt as "The Deadly Assassin" was in its time, I salute him!