First problem, Chaotic Neutral, I wouldn't let just anyone play that alignment. I've known multiple DM's who've outright banned that alignment from their games (along with Evil alignments), because too many players think that CN is a license to do whatever the heck they want and it fits their alignment, being nice and silly one day, and murderous butchers the next.
Second, almost everything from outside the Core Books (and most of the Realms stuff since I run a FR game) is on a case-by-case basis in my game. A lot of WotC stuff is reasonably balanced, and a lot of it is utterly broken. Frenzied Berserker is just overpowered like crazy. The basic concept is acomplished just fine with Barbarian. Why Frenzied Berserker? Just ask the player why he couldn't play a straight-up barbarian, what about that class specifically attracts him?
The player's intentions are a big yardstick here. There are powergaming players I know who I wouldn't let have much beyond the core rules (and then keep an eye on it for abuses). General Rule of Thumb: If a Player is correcting other Players on the best way to mechanically write up their character and chiding them for not being "efficient", or if they first words they use to describe their character involves how insanely high their damage/spells/saves/other stats are, then no.
Case from my own game of something that's case-by-case. I've got a player in my game who has only played 1e AD&D and this is her first 3.x game. She is playing a LG monk, and doesn't like the presumed wealth of 3e and that magic items are largely required at higher levels, she'd rather give all her wealth away in-game and laments having to save up money to buy more things because she considers it very out of character (and has spent most of the campaign giving away most of her money as she got the chance). The player is a great roleplayer who doesn't min-max or powergame. I consider this an optimal case for Vow of Poverty from BoED, since it fits with the character concept, the player is playing the character properly for it, and there appears to be no intent to exploit or bend the VoP rules at all (but I'd be a little nicer than written, an ascetic monk can't have a wooden holy symbol of his deity as written, which is just silly IMO). Normally I'd never allow VoP, but this is the only case I would allow it, so I showed it to her and she's taking those feats as she levels up.