There isn't any fine print in the orders given by the CMA. If the decision stands under appeal then Microsoft will not be able to acquire ABK. It really is that simple.
Until the day they drop the deal and pay the 3 billion to Activision, I will continue to believe they have a backup plan forming.
There wouldn't be a reason to waste time and resources if they didn't have a plan. The plan may make regulatory history, you may not like the plan they have. People in the UK who use Xbox may not like the plan, but there's a chance there is a plan. You can't ignore the fact that Microsoft have been acting strangely about the CMA.
You have two huge companies. One megalithic company. And one massive publisher. Who is run by bobby kotick and wants to be acquired so badly by Microsoft. It wouldn't be outside the realm of possibility that they can create some kind of loophole.
Now don't get me wrong, I think the chance they drop out of the deal vs go through with some shady business is 70% they will drop out 30% shady business. but I think that its really not a non zero % chance scenario like you make it out to be.