Bjorn, that looks promising if a bit complex. I think I've got 256GB of SSD, but I suspect that's not enough for /Windows and / on Linux.
Josh, I think you're right. Perhaps that's the way to go: Linux will be slower than it could be, but it may be easier.
What I don't know is if I can leave everything as it is, shrink the 1.8TB NTSF partition, and use the free space for /, /boot, and /home.
Is it safe to say that writing to the RAID partition writes to both the HDD and the SSD? I'll have to find a description of that, too.