I mean, you can kinda do that already. I have an SSD that I use for holding backups for my phone and photos+videos since I have like over 250gb of photos and videos over the years. I've used the same Google account since my first android phone so I have lots of data accumulated. My USBC to SATA cable and 1tb SSD work great for that. I do have 2tb on Google One also so it's like a backup of a backup lol. Unfortunately I don't see Samsung ever implementing this idea, as they want you to buy the higher storage phones. This would effectively render storage upgrades useless for a certain group of customers. So basically this exists already, just with an extra step, you have to take the video using device storage and then transfer it to the storage device.
