The larger frag stashes are a great idea, I do believe potions should be confined to bronze and silver chests. 1000 loyalty is a lot of days/donated money and to open something for 1000 loyalty, or 55 dots worth of gold and get any type of potion seems a kick in the teeth.
Unless you were to implement some 'overpowered' pots as you put it, Teleport 200, Titan Immobiliser, LF 1500, Conserve 800-900(?), Distil 250-300 for example. All the rewards should greatly outweigh the costs of things such as 'loyalty' points, especially as they're such a rarity (as are the chests). At least the bronze and silver can be bought for a reasonable amount of gold.
Loyalty stashes also great and would help counter the issue above.
Anything to do with Epics is a win, always need more upgradable Epics. If anything to add value to most obsolete Epics/Crystal/SE items!