I think I’ve done it. I now have my own home IaaS.
I went for the OpenStack approach, Packstack with RDO on Scientific Linux. In the future I want to replace SL6 with Gentoo on the bare metal, and install the OpenStack packages from portage, but I’ll wait for the work from a Gentoo dev who knows what he’s doing.
This also means that the running hypervisor is KVM, not the Xen that I would rather be using. Technically, there isn’t much difference to them, but Xen is the hypervisor used by AWS, PV images can be booted without fiddling with partitioning and bootloaders. That’s so ’90s.