Having the disks connected externally is the same as having them connected internally
No, it 1000% is not, especially in the case of USB that I used. Even in the way Linux handles everything as a file and target, it is vastly different.
No RAID solution I know of would lose the array on a power outage
Hardware RAID enclosures have batteries on the disk controllers for this very reason. We aren’t talking about those though, we’re talking about software RAID on JBOD, which wouldn’t have those sanity protections. Here’s some random blog explaining deeper.
Honestly I don’t see how interrupt handling would be any different between internally or externally connected devives, except for different buses/protocols handling it differently intrinsicly
See above
Maybe I’m too spolied by using ZFS, but again I don’t think this would actually be a problem
That’s a filesystem solution to a hardware problem, so yes, probably a bit spoiled there, or at least it’s skewing your understanding of what RAID is and how it works. One of the reasons ZFS exists, actually. It’s nice to have nice things though.
It’s not going to be effortless. That’s not really the goal. Anything that uses Google Play Services is going to be a problem still as the underlying service layer just mocks out those API calls a la Waydroid. They’re working more on the FEX stuff from what I’ve seen in the repos.