Just rewatched the movie, and it got me thinking about how we might actually pull off something like. These are all the issues I can think of, in order of importance; (and in case you were wondering, I am super drunk on a lazy Sunday)
Economy: How would anyone make money from this game? First is the companies who engineer the hardware. Beyond that, I'm not sure. The game appears to be free, so even with stock market value & other investors, what does Gregarious Games offer to justify that investment? The only thing I can think of is the game's Coins function as a cryptocurrency, which can be exchanged for real world money, and by extension food & housing. However, this raises the specter of corruption and 'gold farming'. If a cryptocurrency achieved that level of societal acceptance, it would certainly face government oversight and abuse.
Exploitation: We've seen that 'bot nets' are possible, if only practical on a corporate+ scale. We're told that everybody starts the same. If every new 'life' generates a small amount of Coin (effectively new money), what is to prevent a government-run effort of rapidly creating and killing new accounts/lives, and harvesting the resulting Coin? Inflation would make the real world value of Coins next to nothing in less than a month. Even assuming a less than 100% transfer rate, say 5% of the victim's total, you're still constantly creating money faster than new players come into being. I have no answers here, only more questions about how user accounts actually work.
User Accounts: I'm completely at a loss here. The biggest paradox in this area is when Artemis logs in using an IOI connection. She retains her avatar, but still gets an IOI suit and gear? Does this mean that the player account and the connection used are separate entities? We know that modding is possible, but I don't know of any IRL way to achieve something like this. If they are separate entities, how would Gregarious Games verify that each person is unique, in order to prevent the aforementioned gold farming?
Modding: We've seen that it's possible to create new things in the game, modify existing things, and create a new space. How would this work? Literally every player and their mother would want to make their very own virtual Minecraft realm, to say nothing of other games. The logistics of maintaining a system like this is mind-boggling. Even in modern games, systems for player housing remains primitive at best.
Ok, that's all I've got for now. /rant