It SHOULD be possible (that dangerous word!).
I have two running siduction systems, which have most of the OS on a single ssd, and /mnt/DATA on btrfs filesystems on a matched pair of hdds, (WD1000s). If you can install /boot on another bootable drive, (efi boot partition on a different hdd or ssd), then I think this well be perfectly functional. I doubt that you can boot from a dual-drive btrfs filesystem -- I think you'll need the third drive with efi partition to put /boot on.