Could it be possible to RAID them maybe as one drive? BTRFS does support such a thing, but note that RAID 5 and 6 is fundamentally broken as they are weak to one disk failures; especially considering you’re kinda mixing the home partition between drives from what I’ve gathered.
Do lemme know if my interpretation of the question is incorrect; I’ve just has a coffee so it’s gonna take me a bit to get going lmao.