Technically, there isn't a restriction from a hardware perspective, but there are a lot of different hurdles they would need to get past for this to be ready for primetime. First, storage is going to be a problem--with only 500gig internals, it will be an issue as the drive will need to be partitioned in order to dual boot. (at least that's the only way I've ever done it, that or actually separate drives).
They could just make it so an external harddrive is required to dual boot, but then what percentage of your userbase actually has one? Enthusiast tend to think they represent their market, but in reality we are a small, small group. I have an external and would love dual boot, but for every one of me, there's likely 10 people that have no idea the Xbox One has a 500gig HD and will never come close to using it all.
This is the closest thing to a hardware restriction that I can think of off the top of my head. With that aside, there are a lot of other reasons why MS would not do this--mainly, they would be advertising to buy PC games on their hardware. It's pretty well known that Console manufacturers don't make a large profit, if any, on the actual console itself. Attach rate is king (software sales, etc.), so MS potentially losing money on hardware and then pushing software sales to another market would be suicide. This would never happen, in my opinion.