I am migrating from vios 22.214.171.124-FP24 SP-01 to VIOS 126.96.36.199.
updateios doesn't not work, it complains about missing pre-req filesets because the current base level of the fileset are lower than the required base level ( VIOS 188.8.131.52 is based on AIX 6.1 TL7 SP3 )
( from https://www-304.ibm.com/support/docview.wss?uid=isg3T1011386 )
It is possible to reinstall a VIOS 2.1.1 installation, and remap all virtual devices.
1) Upgrade to VIOS 184.108.40.206 FixPack 25: