This is already being done by some vendors. My Sony Xperia Z1 Compact shipped with a UK image (where things are supposedly freer), was rootable only via a long

This is already being done by some vendors. My Sony Xperia Z1 Compact shipped with a UK image (where things are supposedly freer), was rootable only via a long flashing process that at one point breaks the screen, had an unlockable bootloader, and had a policy keeping /system read-only built into the 4.3 kernel. If one unlocks the bootloader, the DRM keys for Sony-specific extras are lost. I've found root without /system access is good enough for most things. Tibu works fine. ...but isn't it my phone?