My last reponse was from my phone, so didn't really read what your version was.
It's 7-mode I can see that, that article will not apply.
I saw that it's an root aggregte : aggr0, therefore, root_vol cannot be taken-offline. Therefore, plan will be :
1) Boot up, erase all the disks.
2) Create Raid-4 (2 disk) or Raid-DP (3 disk) root vol
3) When system boots , all the rest of the disks will be spare.
4) Do the saniatizaiton job.
I will send you the steps, shortly.