I think this series was a bad idea. The name "Shield Enhancements" kind of forces us to smack a shield effect (damage reduction, miss rate, freeze chance) onto a permanent. This is because any of the "Enhancements" will go into effect once per turn, with stat changes being permanent and stacking, forcing us to use effects that could also work on a shield, but then nerfing it because it works without a shield and we can't have these permanents overshadowing shields. "Shield Synergy" would be a far more interesting series, ie permanents that only affect enemy creatures and have effects that have synergy with the shields of that element.
/offtopic