Greetings,
Imagine my surprise when I hit level 5 and found out I couldn't take Shield Maidens Grace despite having the requirements? In no area (Including the source book) does it mention the need to be a paladin, and whilst on POTM it says "The paladin can channel energy to grant grace and spiritual calm to his companions." the word Paladin is not in the source version. (Though perhaps it could be argued that Shamans dont properly have Divine Grace?) It does mention there 'Spiritual Calm" though, which is very thematic for a Shaman. Paladins dont tend to take the feat (Yes i know some are out there, I took it myself) it is a very underused feat. Shamans have the bonus feats to fit it in, and the idea of using the spirits to share a bonus for a very limited time seems a great fit. It lasts for 2-7 rounds (6+ only if your really pumping that cha) so its still not likely to see a lot of use, but it would be cool to see it out there in the wild for once.
Just sayin, would be cool and thematic.