It's kind of like writing your own paladin's code. Nifty. I really like the idea.

As I was reading I was thinking that some of the Mantles are things you wouldn't want to take without the rest of the PCs' consent. ^^; But then... paladins are kind of like that already, and this gives loads of options. I really don't have any problem with some Mantles being easier to keep than others -- it makes sense that some paladins are going to be more zealous, and are going to get more awesome stuff for it.

You'd really have to have a DM you get along with though. Some of the Mantles' requirements strike me as being fluffy enough to potentially become disputed.