If you have 100M I'll create a company to setup and maintain infrastructure. Though depending on your size I might need more money to maintain yours. Setting up the company isn't hard.

What is hard is doing it today. It will take a year just to figure out the various custom configurations you need to get a majority of users switched over without issue, and there will be a long tail weird cases that will go on for years before everything is done. This isn't unusual - the simpler case of switching my college campus from Coke to Pepsi took over a month and there both vendors cooperated in making it a smooth switch (Coke does not want to burn bridges as this happens all the time and they want to be back again next time the contract comes up - right now Microsoft doesn't have that incentive)

So, no you don't need a "Microsoft-esque" company, you need independent service providers who just know their stuff. Today, a company (any company!) with the proper skills CAN offer setting up and maintaining government infrastructure, independent and sovereign from Microsoft, by using commoditized hardware and open source software, with no long term vendor lock-in.

The offerings do exist, and get some traction. If done right, they should be cheaper in both short and long run, compared to Microsoft licensing.

So, what's holding us back?

1) One element is aggressive pricing for key customers and partners, on the part of the smarter incumbents (in this case Microsoft).

2) Another is a "reverse network effect": Scarcity of talent to create companies like the ones I suggest. And with too little supply, the demand side will be afraid to "not choose IBM" (figuratively).

3) A third is Microsoft 365's real-time collaborative editing. Yeah, really. The needs of some specific users get to dominate decision-making, since the key decisions are pitched in PowerPoint, analysed in Word, budgeted in Excel and distributed using Outlook. A lot of old dogs would have to learn new tricks.

But yeah, somebody really should do it...