Why don't Microsoft do this?
Microsoft are between a rock and a hard place with Surface.
On one hand they are trying not to step on the OEM's toes and have publicly stated the goal of Surface isn't to compete with OEM's but to essentially create new product categories (think for a moment how hard that must be and how often conflicts must arise).
Then on the other hand we have Microsoft showing examples of what is clearly the best design in PC hardware, matched with crapware free Windows, bonuses like OneDrive storage and Skype minutes and great driver/firmware update support.
My great idea they solves the problem; Signature PC v2.
Imagine for a moment if Microsoft put all their design effort into creating a range of devices; it's hard to argue the Surface Pro 3 design wouldn't adapt to making the best AiO and notebook range available. Then instead of making these devices themselves simply hand it all over to the OEM's.
These "signature" PC's could then be paired with bonus OneDrive storage, a clean version of Windows and guaranteed updates. OEM's could be incentivised with a greater marketing budget for joining the program.
Here's the kicker... there's no reason they couldn't be branded as "Surface PC's" and sold in the Microsoft Store and select retailers.
That way it wouldn't matter if you purchased a Samsung, Asus, Acer or Lenovo "Surface PC" because you know they would all be quality devices.
This isn't rocket science (I'm sure others here in the Tribe have had the same idea) so the question is why don't Microsoft do this?