That would lower the barrier to entry significantly. It doesn't address the issues with the bios but someone mildly adventurous would have a much easier time going forward.
I think something like that would have to be sponsored by and maintained by a big distro though. I'm afraid if it was a community effort the amount of bikeshedding would stop it before it even began.
The order doesnt matter as long as they are the same drives, you dont have a usb dock or raid card in front of them (ie sata/sas/nvme only)and you have enough of them to rebuild the array. Ideally all of them but in a dire situation you can rebuild based on 2 out of 3 of a Raid Z1
You can do that, you shouldn't but you can. I've done something similar before in a nasty recovery situation and it worked but don't do it unless you have no other option. I highly recommend just downloading the config file from your current truenas box and importing it into a fresh install on a proper drive on your new machine.
Sort of already mentioned it but you can take your drives, plug them into your new machine. Install a fresh Truenas scale and then just import the config file from your current setup and you should be off to the races. Your main gotcha is if the pool is encrypted. If you lose access to the key you are donezo forever. If not, the import has always been pretty straightforward and ive never had any issues with it.
Lots of people virtualize truenas and lots of people virtualize firewalls too. To me, the ungodly amount of stupid edge cases, especially with consumer hardware that break hardware passthrough on disks (which truenas/zfs needs to work properly) is never worth it.