Back to the days I was fixing a lot of computers of friends and relatives, my Swiss army knife of Linux was https://www.system-rescue.org/
Very lightweight but with a full set of recovery tools. I've tried it recently and I still find it up to the expectations.
I've also used a fair amount of https://clonezilla.org/ to (re)store images of freshly installed OSes (mostly windows XP and 7 to give you an idea of the timeframe) for people who I know would have messed up faster.
QNAP sells extensions unit https://www.qnap.com/en/product/tr-004
They usually connect with USB (at least for home grade devices), but my understanding is that they are not seen as block devices so the nas has access to all the single drives like they were internal.