But this is unrelated to how this limitation hurting OEM in making feature-packed devices to stand-out from first-party devices(I feel that's part of the reason HTC/Samsung quit the market). This two point of view are different and can be discussed separately.
I'm not sure I understand exactly what you think should be discussed separately. We're discussing two capabilities:
a) Microsoft's technical capability to distribute insider preview updates to every W10M device (
no matter which OEM built the device)
b) Microsoft's technical capability to distribute official updates to every W10M device, largely without interference by carriers (
no matter which OEM build the device)
both of those capabilities
absolutely necessitate a standardized hardware and software platform, i.e. one where OEMs
aren't capable of willy-nilly modifying the code base and rebuilding their own device-specific version of W10M. As soon as an OEM introduces such OS customizations, MS looses the ability to update those devices directly, because MS' OS update packages don't contain the device specific customizations the OEM made.
Either way, I can assure you that allowing OEMs such "freedoms" now would change absolutely nothing. Not a single OEM would re-enter the WM market, much less engage in such expensive development/customization efforts. Neither HTC nor Samsung quit WP/WM for this reason either. Both companies quit the market because they simply couldn't sell enough devices to make it worthwhile. If OEMs can sell enough devices to make it worthwhile, they won't pass up the opportunity to make more money, and will re-enter the market, with or without such "freedoms".
In fact, at this point in the game, the exact opposite is true. Giving OEMs an OS they can install onto their phones (in the same way you can install Windows onto a white-box PC), along with a few pre-built drivers for standard off-the-shelf hardware (like camera modules, etc.), is the only shot WP/WM has with other OEMs. The cheaper it is to build a W10M device the better, although currently it doesn't matter either way. Even if it cost OEMs only $1 to build a W10M device, it's still a bad deal if OEMs can't sell it... currently.... they can't.