Not sure if irregular booting is still an issue, but that sounds a lot like device names changing between boots. If I could hazard a guess - you've got something like /dev/sda in your fstab, where ideally you'd have UUID=1234-ABC. You can get the uuid by running
That... Is literally how you do it. You install the system onto a subvolume. Or many, in fact - the way I do. Root, var, srv, home, opt all get their own subvolume. Only boot stays as a separate partition.
Ahem... What? Is this a Robert -> Bob kind of thing or something else?