I am going to float an idea that I think is extremely unlikely, but I'm posing it just as a kind of "what if?"
Berkshire Hathaway buys Infinity Ward and/or Treyarch, along with all rights to future CoD console and PC games. The Microsoft gets COD mobile rights, and maintains rights on existing COD games. The deal closes.
I do think that the CMA would accept this structural remedy. Additionally, Berkshire Hathaway really doesn't have a dog in the console war fight, or real potential antitrust issues that I am aware of. They certainly have the wallet to support the project.
Berkshire Hathaway owns over 60 million shares of Activision, valued at several billion dollars. If the deal goes through, those shares increase in value by more than $1 billion, whereas they have the potential to lose substantial value on the deal failing. The future rights to COD for consoles and windows would ostensibly cost less than the full bundle of rights with respect to COD. Microsoft would immediately get a library of current and old COD games to market on Gamepass, along with the rest of ATVI.
Warren Buffet has a nose for opportunity, has built his career buying and selling large or controlling interests in companies, stands to profit from the deal going through, and has a penchant for approaching businesses with a "take it or leave it" buyout offer. If Microsoft wants this deal to go through, they might take a discounted price on this portion of the business.
I don't know if Buffet will make an offer, or if it will be at a price that Microsoft deems worthwhile. It's just a thought I had, and sort of an interesting proposition. There aren't a ton of companies that have the money readily available to buy this franchise, coupled with the ability to do so without antitrust concerns. Berkshire Hathaway is one of them, and they have the added incentive of being a substantial Activision shareholder.