Idea for a game using bitcoin as a currency

We need a game like World of Warcraft (any MMO could do this), but using Bitcoin as an in game currency.

World of Warcraft already has its own in game currency that they control, as does every other game like it, so games that are already established will be reluctant to switch, but...

What if we created an all new game that inherently uses bitcoin (and maybe also steem dollars!) for its transactions?
Users could buy and sell their gear from other players, in an in game store with a real transactions.

A user who gets lucky and gets a rare item in game, could sell it for legitimate currency. Similarly, a user who wants to get a rare item, and has some spare cash, could purchase the item in game from another user.

Here's one idea of how it might work:

Users pay a small amount to play each month. (like 1 to 10 mBTC)

Users can do quests, strikes, raids, whatever and get gear from those. Common gear would be common, and rare gear would be rare.

There are two main types of gear. Common gear and rare gear. Rare gear would be better, but can't be sold to NPCs. (NPCs are poor)
Common gear could be purchased from and sold to NPCs for some fixed amount of satoshis. (e.g. common gear would be very cheap)

You'd have to make it so that users couldn't make money from the game hosting company, probably by limiting how much they can sell to NPCs to the amount they payed to play. (e.g. I can't sell gear worth more than 10 mBTC over the course of a month.)

But good players could easily make money selling rare items to people willing to buy them instead of grinding for the items themselves. Meanwhile, the hosting company could make money through the monthly memberships, in-game ads (like on virtual billboards), etc.

They could also make money by having rotating, limited sets of rare items be sold by NPCs. (But not the really rare items, just a small subset of the rare items)

Anyway, I think it would work. It could work for any MMO type game, and it could help add some stability to the digital currency market!

Also, yes. I am aware that there are some games already doing this. They however are not MMO games, and I think that an MMO game would be a better fit.