If I was Microsoft.
1. Drop out of this deal. It's a waste of resources and it doesn't seem to be happening. Cut the loss and move on.
2. Before the ink dries on the deal cancellation immediately start reaching out to third parties about exclusivity and game pass deals.
3. Start compiling a list of small-medium sized studios/development groups such as CDPR etc. that would not require much regulatory checks and start making offers to acquire now.
4. Any acquired studios will fall in line with Bethesda. No release on PlayStation. Forgo any potential PlayStation sales in hopes people will buy Xbox to play these games and it will shift marketshare in Xbox's favor. All games Day One Game Pass and all past games on the service too.
If they spend 2 more years trying to appeal this transaction and don't also improve the current first party output... well...
RIP Xbox IMO