The only solution I can see is to break Microsoft up. Four companies - one gets Azure and no software products. One gets Office, nothing else, and they're not allowed to do any cloud services. One gets Windows, nothing else, no cloud. Last company gets everything else, no cloud services, no Windows, no Office.
None of the four are allowed to share staff. They're not allowed to buy software directly from each other but most go through the channel. The other 3 are strictly forbidden from using the first's cloud services for any purpose.
Draconian? Yes. Will it make anyone feel any better about things? Doubtful. Will it solve anything? Probably not. Will any politician dare to do it? Of course not, Micros~1 will donate far too much to make sure it never happens.