This is the approach I take.Or maybe just don't do sensitive things on your phone.
... unless you like removable batteries and card readers. ~
Google ain't the good boy they're made out to be.Now that google is pushing monthly updates I think we are seeing who is going to put the effort in to keep up to date and shame those that don't. Google knows that many won't so that's why they made the patch level visible in about phone, and if a manufacturer is hiding that we know it's not good news.
Ironic that Google is "enabling" guys like copperhead instead of fixing the problem themselves.
Android is an open system running on relatively open hardware that's largely manufactured by the lowest bidder in a country with a monolithic security apparatus. There are going to be exploitable flaws everywhere. You could probably flash Ubuntu or NetBSD onto your phone but you'd be giving up minor conveniences like LTE and most of the cloud functionality.
Or maybe just don't do sensitive things on your phone.
I don't think there's such a thing as a big enough battery. Maybe if it lasted a week or something. I find that I can go two days without charging if I ignore the fact that I have my phone, but if I'm shooting video I'm only going to get ~4 hours out of it no matter what I do. And I'd rather pause and slap in a new battery than be tethered to an external battery or giant clunky battery charging case.
Storage? Again, no such thing as too much. My phone has a 200GB card in it. I'm "only" using about 2/3 of that, but as a device I know I'll always have with me, it's definitely a useful place to put things.
The ergonomics alone of shooting 4 hours of video with a phone just buggers the mind. Do you have some special mount or robot arms?
I put my phone on a short lanyard that falls around my sternum. I walk around the entrance to a comic book convention. I've never done four full hours of video but I've done more than two several times and I could see going longer if I didn't want to go do other things. Even two hours of video recording has a pretty serious deleterious effect on my battery though.