Ability to allow players to safely make Bitcoin transactions within the game.

Just a friendly word of warning…

I urge you not to make a game where players can earn items and sell them for real money.
This usually ends very badly for the game, where most of the player base actually aren’t even human anymore.
Take the RMAH (real money auction house) in Diablo III as an example of this…
Blizzard eventually had to shut it down because they realized that nobody was actually playing the game anymore.
It was just a bunch of bots, utilizing advanced algorithms to try and turn a profit.
And a lot of these bots can (potentially) eat up bandwidth faster than most human players can, resulting in company money going into either supporting or trying to detect & ban these bots.
And all talk of botting aside, there will be an even worse group of human beings who will continuously attempt to scam other genuine players, which could easily become a liability issue for the company.

Of course, that’s not to say that you won’t turn some sort of profit with this business plan.
As a matter of fact, if the game itself is good enough, I’m pretty sure you will.
But it really does become more of a headache in the long run.