It's not a gross simplification. It's a given that there is luck invovled in any sort of threatening situation and yes, there are things you can do to avoid those types of situations. My comment was based on if you were forced to get physical in such a situation that the average thug would probably be on the sore end when faced with a skilled Aikidoka who applied the proper tech and executed it properly.
By my estimation you a grossly over complicating it.
How is it a gross overcomplication to ask, "who do you actually think you're fighting and why have they attacked you?" Violence comes in many different forms and the assumption that there is a one-size-fits-all solution is a very dangerous one to make. It's a bit like talking about how to survive an "average car accident". It makes a significant difference whether you're talking about getting knocked down at a crossing or being in a 20-car pile up on a highway.
Let me give you some realistic violent situations:
1) Two muggers with knives want your wallet
2) A drunk guy's picking a fight with you to show off to his mates
3) A group of bikers have taken offence because they think you're misbehaving in "their bar" and aggressively tell you to leave
4) A group of teenage gang members have surrounded you and start "messing with you" in a parking lot
Which of these is your "average thug"?