Failing ZFS Raid-Z2, need to build new pool but lack a SAS port. Can I disconnect one drive from Raid-Z2?

I have a Raid-Z2 pool with 6 * 4TB drives. All the drives have a bit over 40 000 hours running time. Now they all seem to be degrading at the same time. The pool is degraded, and all drives are marked as degraded with to many errors. But luckily no lost data at the moment.

        NAME        STATE     READ WRITE CKSUM
        File        DEGRADED     0     0     0
          raidz2-0  DEGRADED     0     0     0
            sda     DEGRADED     0     0     0  too many errors
            sdb     DEGRADED     0     0     0  too many errors
            sdc     DEGRADED     0     0     0  too many errors
            sdd     DEGRADED     0     0     0  too many errors
            sde     DEGRADED     0     0     0  too many errors
            sdf     DEGRADED     0     0     0  too many errors

I would like to build a new pool with Raid-Z1 and 3 * 6TB drives as I don’t need all the space as in the original pool. My problem is that the old pool has 6 drives and my pool will have 3, but my SAS controller only has 8 ports. So I would like to disconnect one disk from my Raid-Z2 pool, connect my 3 new drives and create a new pool with them and then save my data by copying to the new pool before the old pool fails.

Is that possible? My thinking is that the old pool should work with one disk missing. But when I tried disconnecting a disk I’m unable to access any data in the old pool.

Anyone know how to solve this?