The permissions approach isn't bad. I may trust Thunderbird for some things, but permission to read SMS and notifications is permission to bypass SMS 2FA for every other account using that phone number. It deserves a special gate that's very hard for a scammer to pass. The exact nature of the gate can be reasonably debated.

That's hand-waving away quite a lot. The task changes from serving a copy of a file on disk, as every other image format in common use, to needing a transcoding pipeline more akin to sites like YouTube. Technically possible, but lots of extra complexity in return for what gain?

Draining the pipes isn't that simple, and even if you did, you still have things like a water heater, toilets, softeners, filters, and expansion tanks. You also wouldn't get the water sitting in drain traps; winterizing a house or RV involves pouring a little RV antifreeze down each drain.

AI has processing delay even if run locally. In telephony the delays are more speed-of-light dictated. But the impact on human interactive conversation is the same.