I'd say it is somewhere between 5 and 6, maybe closer to 5 than 6.
Potion is sort of like a Silver and a half, so I'd price it at $3P.
I feel that this card may be a bit redundant with TR and KC out there, it's also a bit hard to price because it's a one-shot.
It may be superb when you draw it with Wharf and not so good when you draw it with Pawn. Then you have to decide whether you want to spend this card on a mediocre action or wait an entire shuffle for something better to draw with it.
Other one-shots like Feast, Embargo and Treasure Map have the same results every time you play them.
I'd give it a twist to remove the one-shot aspect, for example:
You may discard up to (2? 3? 4?) cards from your hand. If you have discarded any cards this way, you must choose an action card from your hand and play it as many times as the number of discarded cards or reveal a hand with no action cards.
This way, it still presents a choice to players, but they have to pay more for better effects, it also works as a voluntary discarder if someone wanted to play a Library.
You could also let the number of times you may play an action card depend on the number of empty piles, like City.
E.g.: You may choose an action card in your hand an play it twice. If there is one empty pile, you may choose another action card from your hand and play it; or if there are two empty piles, you may choose another action card from your hand and play it twice.
Keep in mind that both are just examples, but I'd be fun to provide some variable way to supercharge your cards, other than another fixed one-shotter, but that is just my opinion. I won't intrude on your idea further.