The limitation is that CoreMediaIO plugins still run in-process (and not just in some daemon but in arbitrary application processes!), when Apple's direction for over a decade has been to move all plugin mechanisms towards an out-of-process model. There's nothing about video plugins in particular that would prevent them from being out-of-process; in fact, most of Apple's CoreMediaIO plugins already have the bulk of the logic in a separate "assistant" process, but the IPC layer is reimplemented by each individual plugin rather than being done generically by CoreMediaIO itself. It's clear what has to happen, but Apple hasn't done it yet.