ZFS pool restructuring and emergency repair

[Quartz]

> - A server is set up with a pool created a certain way, for the sake of
> argument let's say it's a raidz-2 comprised of 6x 2TB disks. There's
> only actually ~1TB of data currently on the server though. Let's say
> there's a catastrophic emergency where one of the disks needs to be
> replaced, but the only available spare is an old 500GB. As I understand
> it, you're basically SOL. Even though a 6x500 (really 4x500) is more
> than enough to hold 1Tb of data, you can't do anything in this situation
> since although ZFS can expand a pool to fit larger disks, it can't
> shrink one under any circumstance. Is my understanding still correct or
> is there a way around this issue now?

So I take it that, aside from messing with a gvirstor/ sparse disk 
image, there's still no way to really handle this because there's still 
no way to shrink a pool after creation?