Hacking the Nexenta boot disk

So far on my Nexenta NAS boxes I have the boot disk on a 16G USB memory stick which seem adequate but I want to try and see if I can relocate the boot disk to a partition of the SSD that I am using as a ZFS L2ARC cache device. Unfortunately the default Nexenta installer will not allow installation to a partition of a disk, and there will also be a problem with later trying to use another partition as the cache device. However, I want to try and dive under the hood and mirror the USB key to a disk partition and then to manually add another partition to zpool as a cache device