This is such an unbroken concept I dont understand why people dont understand 
Come on, in the examples just provided I am guessing you mean he could do any one of those things. They take a pile of feats and just the right conditions to happen.
First, someone has to do something dumb within range. Likely a 5' step would have negated this anyway. Anyone with tumble would ignore you. Anyone who can get some cover would also ignore it.
Second, the attack might miss. Sure, this actually does happen sometimes strangely enough.
Third, the attack has to do sufficient damage to take out the opponent. This happens less and less often at higher levels, people tend to get a lot of hp.
Fourth, the guy has to have cleave. This is not exactly a common occurance even for fighter builds. The feat is useful at low levels but drops off in usefulness rapidly.
Fifth, he has to have an aoo remaining. If people are being this dumb often then he probably wont. And combat reflexes is even less common.
Sixth, there has to be another guy within range to attack with his new attack. This can also be a problem. Strangely enough not everyone just stands around in small groups as that can bring dissaster from numerous sources. Also, there is always just something about sending all the mooks in and then the big bad coming all by himself, happens all the time in movies
Seventh, the attack against the new target has to hit. Yet again, sometimes these things miss.
If instead one wishes to use some other combat option instead then that will take even more feats.
Effectively, all of this for an attack that might happen in very rare cases making a fairly lack luster feat just a little better sometimes.
Once again though, it is one guy taking advantage of the situation, not another guy being punished. While it is a situation that would not have happened if someone hadnt been dumb it is also something that most people would not be able to do anything about. It is only the guy with this specific feat who can even try anything at all. It is a bonus associated with this feat, a bonus that it gives directly.
As for now allowing combat feats outside of ones turn then I guess you also dissallow things like trip on an aoo. That is fine, it is your game, but I think it is a serious flaw in your reasoning.
While turns are very organized and such it is emulating something where everything is happening at roughly the same time. This means that things happening 'outside of your turn' merely mean 'outside of your sequence in initiative', they arent just standing there like idiots and drooling, they are constantly moving and shifting and doing whatever it is that they do. In this case it makes even more sense because the outside observer simply cannot tell whether it was one of your 'iterative' attacks or an 'aoo', they are both swings looking for openings. To instil even more artificialness into the system all in hopes of stopping an incredibly rare event from happening that isnt exactly incredibly powerful to begin with.. well.. that just seems wrong. Horribly, horribly wrong.
Come on, in the examples just provided I am guessing you mean he could do any one of those things. They take a pile of feats and just the right conditions to happen.
First, someone has to do something dumb within range. Likely a 5' step would have negated this anyway. Anyone with tumble would ignore you. Anyone who can get some cover would also ignore it.
Second, the attack might miss. Sure, this actually does happen sometimes strangely enough.
Third, the attack has to do sufficient damage to take out the opponent. This happens less and less often at higher levels, people tend to get a lot of hp.
Fourth, the guy has to have cleave. This is not exactly a common occurance even for fighter builds. The feat is useful at low levels but drops off in usefulness rapidly.
Fifth, he has to have an aoo remaining. If people are being this dumb often then he probably wont. And combat reflexes is even less common.
Sixth, there has to be another guy within range to attack with his new attack. This can also be a problem. Strangely enough not everyone just stands around in small groups as that can bring dissaster from numerous sources. Also, there is always just something about sending all the mooks in and then the big bad coming all by himself, happens all the time in movies
Seventh, the attack against the new target has to hit. Yet again, sometimes these things miss.
If instead one wishes to use some other combat option instead then that will take even more feats.
Effectively, all of this for an attack that might happen in very rare cases making a fairly lack luster feat just a little better sometimes.
Once again though, it is one guy taking advantage of the situation, not another guy being punished. While it is a situation that would not have happened if someone hadnt been dumb it is also something that most people would not be able to do anything about. It is only the guy with this specific feat who can even try anything at all. It is a bonus associated with this feat, a bonus that it gives directly.
As for now allowing combat feats outside of ones turn then I guess you also dissallow things like trip on an aoo. That is fine, it is your game, but I think it is a serious flaw in your reasoning.
While turns are very organized and such it is emulating something where everything is happening at roughly the same time. This means that things happening 'outside of your turn' merely mean 'outside of your sequence in initiative', they arent just standing there like idiots and drooling, they are constantly moving and shifting and doing whatever it is that they do. In this case it makes even more sense because the outside observer simply cannot tell whether it was one of your 'iterative' attacks or an 'aoo', they are both swings looking for openings. To instil even more artificialness into the system all in hopes of stopping an incredibly rare event from happening that isnt exactly incredibly powerful to begin with.. well.. that just seems wrong. Horribly, horribly wrong.
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