Forrester said:
Jesus f'ing christ . . . sure, you're not a troll. That's what Bugaboo says all the time, too
.
Actually if anyone is trolling it sounds like you.
This isn't rocket science. Step away from the rules for a second -- you're arguing that if someone standing 5' to my right shoots a bow, he's putting my life in jeopardy if there's a Cleaver in front of me. We're not the ones that need to suspend disbelief. Neither are we the ones with "logic" problems.
How is this any different if someone is just standing next to you and they're killed during the normal attack iteration, thus putting your life in jeopardy because there is a Cleaver in front of you.
Let's take a look at your logic for a second. You are basically stating that you have two attacks that are exactly alike (same attack bonus, same weapon, everything), except in one instance if you happen to kill the foe you're hitting you can attack someone next to you for free, however with the other you can't. Not very logical to me. You are too hung up on what causes the attack, not the attack itself. What causes the attack has nothing to do with the attack.
Let's say I'm the fighter and for what ever reason I can't damage one creature (DR, High AC, whatever). Now I'm really concerned with killing creature two, so I'd ready my action to say that when monster one dies, I charge monster two. Simple example of when monster one dies, monster two gets attacked. Now according to your logic I can't do this, because the only reason monster two was attacked is because monster one died. What makes people have to
suspend belief is when you have one situation where
x occurs, but in the exact same situation
y occurs. Unless magic is involved that is when my bs alarm starts to act up.
Going back to the rules -- the problem is that AoO/Cleave allows you to attack someone with an AoO that did not draw an AoO. The entire POINT of drawing an AoO is that you've left your guard down. In your little system, one can take an AoO against someone that does NOT have his guard down.
You aren't getting an AoO against that person. You're getting an attack. But wait I see what you're getting at, during the normal attack action
ALL the defenders around me drop there guard so I can take swings at them.

Otherwise they wouldn't have there guard down when I killed there buddy next to them making me unable to cleave them. Again who's trying to suspend belief here?
An excellent compromise -- and one I've used -- is to allow AoO/Cleave *only* against foes that are drawing AoOs themselves.
For instance, let's say that the Cleaver is facing off five orcs -- they have surrounded him. The orcs realize that they're fighting Conan, shout "


!", and try to run like hell -- not take a double move, but just flat-out run. (Hey, orcs are dumb.)
In this instance, I'd allow AoO/Cleave. If the Cleaver brings down the first orc that runs, he can follow through and attack the next of the four, and so on.
And how often does this come up in game play? It sounds like this would only come into play when you are moving a large number of opponents at once. It also sounds like there could be alot of upkeep for this as well. Case in point. You have your 8 orcs surrounding a fighter similar to the last situation:
Orc 1: Runs away (AoO) and is killed
Orc 2: Attacks Target
Orc 3: Attacks Target
Orc 4: Attacks Target
Orc 5: Attacks Target
Orc 6: Attacks Target
Orc 7: Attacks Target
Orc 8: Realized that Fighter is in trouble so he draws his bow and shoots at the Wizard (AoO). So now the Fighter gets his cleave attempt.
Definitely a lot of house keeping for this to work.
Is it starting to make sense? Finally?
Nope, you sound like you're ranting.