Thanks for the compliments. I'm glad that, if nothing else, the book is helping people make new and interesting characters.
As for feats, Blacksad has it right. Gaining a feat for 1 HrP is really cheap, especially since antimagic usually doesn't come up too often. However, if you do want to have a restriction, you could try making the bear spirit turnable. Maybe, if a cleric turns, rebukes, or commands the bear spirit (which would be considered to have Hit Dice equal to your character level), you'd lose your powers for the duration of the turning. Also, your powers would be suppressed in an antimagic field, but dispel magic would probably only affect one ability, and would just suppress it for a little while.
I'd say that'd be worth a 2 HrP reduction, since, though it's a big drawback, it is unlikely a common NPC would think to turn you. Also, it would probably be okay to have this reduce the cost of a feat by 1. This hasn't been playtested, but I think it should work. However, I'm considering that Gain Feat should be changed a little. Each feat would cost 2, so if you have 5 feats, Gain Feat would be a 10 HrP power, which you could not take until 7th level. This would also mean that the restrictions would reduce the cost only once, instead of once per feat.