That's why I think you'd have to do something board-level at least, not just plugging existing modules or SSDs together. You'd have to stuff flash chips on a novel board with a novel controller architecture.

The work I've seen at places like Samsung and Intel is chip level.

Why hasn't this been done already? No market until recently. Existing flash is fast enough for SSD use cases, and making it fast enough to compete with DRAM makes it more expensive. Meanwhile it's not a true DRAM replacement because it's slow to write, slower than DRAM for true random access, and can wear out with many write cycles. It only makes sense for applications that are read-mostly, streaming, and require huge data, and that was a small market until AI.