Sorry for the necro. But while I was looking these old threads, this one come up. I watched the movie (awesome, by the way), and while I think that no sane DM should allow these feats, Critical Momentum has some potential if rewrite and balanced. I come up with this:
Critical Momentum (Combat, Critical)
You learned to use momentum created by a well-landed blow to dispatch your foes.
Prerequisites: Critical Focus, base attack bonus +11.
Benefit: Every time you confirm a critical hit, you can immediately make another attack. This attack uses the same base attack bonus of the attack that triggered it, but has a -5 penalty if the weapon's base critical multiplier is x2, or -2 if the base critical multiplier is x3. If the weapon's base multiplier is x4 this attack has no penalty.
Special: You can only apply the effects of one critical feat to a given critical hit unless you possess Critical Mastery.
I'm not so sure if I would add this:
"This feat can only be used one time per turn for every +5 BAB you possess."
You see, the original feat is neat, just had some balance issues on the number of attacks made. Making the extra attacks harder to land resolve part of the problem, but I did'nt wanted to make it a wasted feat to those who doesn't uses large critical ranges. If it still too good, add the limit on the number of attacks made. If it became too nerfed, exclude the Critical label. Or another combination...