Thanks Frans,
VIO isn't an option right now. I dug a little deeper into this with IBM and HDS/SUN. HDLM v5.9 apparently provides support for boot disks among other things.
HiCommand Dynamic Link Manager (for
AIX) 5.9.0-01 New Features and Enhancements
[5.9.0-00 Additional Functions and Modifications]
(1) Environment in which the MPIO device can be managed by HDLM are supported.
(2) Environment in which the boot disk can be managed by HDLM are now supported.
(3) Command Device, Swap Device, and Dump Device have been added to the supported storage subsystem of Hitachi.
I hope to get my hands on this version soon and will install and test and post any findings here.