This is a simple idea. A currency mod that can be changed easily, evented in easily and overall not that hard to use.
First, you would have the 'currency' related as just a number. To check how much of the currency you have, you would say "/check" and it would say in the chat.
When the add-on is enabled, in the admin control panel it would allow you to change the name of the currency. When you receive currency, it displays a message on the bottom of the screen "You've received x amount of x!" or whatever.
Now with eventing. There will be addCurrency, removeCurrency, checkCurrency, setCurrency, spendCurrency, onBuyFail and onBuySuccess.
addCurrency adds a specific amount of the currency you set.
onBotKill>Player>addCurrency>100
onActivated>Player>addCurrency>100
removeCurrency removes the specific amount of the currency you set.
onChat>Player>removeCurrency>50
onPlayerTouch>Player>removeCurrency>50
checkCurrency prompts a message that shows how much currency you have.
onPlayerTouch>Player>checkCurrency
setCurrency sets the specific amount of the currency you set.
onProjectileHit>Player>setCurrency>0
spendCurrency removes a specific amount of money and activates whatever you choose the event to do. If you don't have enough, it won't allow the event to activate.
onActivate>Player>spendCurrency>1000
onBuyFail activates when you don't have enough money to spend.
onBuyFail>client>bottomPrint>"go away!"
onBuySuccess activates when you do have enough money to spend.
onBuySuccess>Player>additem
onBuySuccess>client>bottomPrint>"Thank you for your patronage!"
And that's my idea!