You may overpay for this card. Gain one coin token for each 1 you overpay.
+1 Card, +1 Coin Token
This is a foil to the Guilds card Masterpiece, which is a poor card on its own, but allows to you overpay to put a Silver into your deck for each amount overpaid.
It's called Playwright because coin token cards traditionally are people, and it seems plausible for a playwright to produce one amazing work and then be only marginally valuable after. What I like about Masterpiece is that it's a viable buy for 7 coins, the 'deadzone', without being board-defining.
Playwright fixes the deadzone problem doubly - it gives you something worth buying for 7, gives you enough coin tokens to prevent issues in the future, or set up for a megaturn.
This card cannot be bought normally.
You may gain this card when you trash a victory card.
1 VP, +1 Money.
You may gain this card when you trash a card worth 6 or more.
3 VP, +1 Action, +1 VP chip.
Dig Site is intended to give some purchasing power when you trash an Estate, or Overgrown Estate, or beef up Silk Road without much drawback. Museum is a late game vehicle to convert Golds into Victory Points, and it's not a dead card if it ends up in your hand.
Farmland combos brilliantly with either of these cards.
These cards push the bounds of the original game a bit because there's usually at least ten non-basic cards that can be bought in a game. If there's a card with a special gain condition, like Prize, or Madman, it's placed in the game as an attachment to an existing card (Tournament and Hermit, respectively). These could be attached to an... Archeologist card?
The creator of Dominion has said he's not interested in making more cards because the game is complex enough with 220+ cards across all the sets. However, I feel like there's still room for expansion in the single-player mode that's playable online, much like how there are special cards and conditions that are only in Hearthstone's Naxxrammas fights.