The problem is that the content of the device tree isn't really stable -- if a new kernel version has a driver with a new required parameter for instance, suddenly your ROM device tree is out of date and much less useful.
However, there is a fatal flaw in the process that makes this a pipe dream in reality. In Linux, these rules only apply to reviewed and merged drivers. And during review any new DT interface will almost certainly be bikeshedded in some way.
So unless your chip vendor has upstreamed ALL their drivers before a device is manufactured, the device's firmware-provided DT will very likely work only against a vendor kernel and requires updating.