I think in this contest flavor has an important role.
I’m from Brazil, so I chose the currency to be fruits of my country. They really were one of the currencies here in barter times, at the same time of castles and knights in Europe. So, they have a similar flavor to Hinterlands expansion cards.
Here’s my entry:
TROPICAL FRUITS • • Treasure
$1
Choose one:
+1 Coffers; or
+1 Villager.
FRUIT MIX • • Treasure
+1 Buy
When you play this, it's worth $1 per different named treasure you have in play (including this).
It’s a split pile with 5 Tropical Fruits over 5 Fruit Mix.
EDIT: DUE TO FEEDBACKS, I CHANGED MY ENTRY TO: TROPICAL FRUITS • • Treasure
Choose one:
+1 Coffers; or
+1 Villager.
FRUIT MIX • • Treasure
When you play this, it's worth per different named treasure you have in play (including this).
If it's worth or more:
+2 Buys.
It’s a split pile with 5 Tropical Fruits over 5 Fruit Mix.
(Following comments also edited to reflect the new version)
TROPICAL FRUITSA Copper with a chosen bonus, a Coffers or a Villagers, which has big versatility, enabling good resources control. You can choose either use payload now, save payload or save actions.
Though it is a Silver+ at $4, since it is in a split pile with a more expensive card, it doesn’t have the main problem of Silver+ at $4, according to DXV:
The main problem with Silver-with-a-bonus for $4 (for games where people want Silver and aren't gaining it with a Silver-gainer) is that the pile just automatically empties. It's also not great that then you have that bonus in your deck, but didn't care about it at all, weren't making a decision there.
Besides that, it is only a Silver+ because the choice you have. When played it’s not a Silver plus something, it is either only a Silver or a Copper plus something.
Anyway, this issue about Silver+ at 4 seems overcome since Patron.
And in this case, you still may want to buy a silver to give variety to Fruit Mix. Tropical Fruits being a better choice than Silver in many cases also helps to buy them fast to reveal Fruit Mix sooner.
FRUIT MIXA Bank variant which cares for treasure names and gives an extra bonus of +2 buys if you align four different treasures. The split pile itself has two different named treasures, so without other alternative treasures in kingdom it may worth up to $5. It may shine with these other treasures in kingdom, with Platinum and even sometimes be very strong with Capitalism, but it’s the same with Bank.
It’s a Bank variant but plays very different from Bank, since variety is tough to achieve. With four Coppers and Bank your Bank worth $5. For the same result with Fruit Mix, you would need five different treasures. It is more in the spirit of Cornucopia cards than Prosperity cards.
The +Buy bonus ensures you a best benefit from your additional money if it’s worth $4 or more. It is given only from $4 to more to avoid the situations in which it could be a clearly better option than Gold at the sime price. Being a card that prizes variety, this feature of an extra bonus for the challenge to achieve more variety seems to fit it very well.