Is it really a good idea, to make the shadow walk ability for halflings only as a feat possible? I think that kills a lot of the Birthright flair.

Most Halflings will loose the ability, because a feat is so expensive. The whole game-world will be changed. IMagine, there may be some Halflings (with the feat) that play the role of a "scout" in their community.

I propose, give them the feat for free. It's only fair compared to the elven or dwarven abilities.