(Pathfinder) Quintessential Barbarian II feat question

[nick_crenshaw]

The following feat was originally from Quintessential Barbarian II and I'm wondering a couple of things:

1) How good of a feat is it in general?

2) Should/could it be used in 1st Edition Pathfinder?

3) How difficult would it be to convert to Pathfinder, if at all?

Controlled Fury
Early in your adventuring career, you were a barely controlled animal, a predator in human skin whose raging fury
shook the heavens. Now, however, you have learned to tightly control your emotions; though you are still capable
of entering a state approximating rage, your spirit is no longer in torment.
Prerequisites: Ability to rage.
Benefits: You retain all barbarian class abilities even if your alignment is lawful and can freely gain new levels in
that class after your alignment change.

[aglondier]

The question really is, are alignment shifts common in your game? Or are you planning to take monk or paladin levels for your barbarian?
The feat doesn't change anything mechanically, so will translate across systems without effort.
If your barbarian got a helm of alignment change, this feat would be vital. Be great for the story element as well.

[Rynjin]

It'd be a pretty bad Feat, but it wouldn't be difficult to convert. But what you should really do is just...attack the problem at its root instead. Abolish asinine alignment restrictions. Unless there's a god involved, it doesn't make any sense for a class to have them.