The code already looks for "linux,usable-memory" in preference to "reg". Can you use that instead?
That would have the advantage that existing kernels already understand
it.
Another problem with using "status" is we could have device trees out
there that have status = disabled and we don't know about it, and by
changing the kernel to use that property we break people's systems.
Though for memory nodes my guess is that's not true, but you never know ...