PXE boot to ISO file

This should be possible with ipmitool. Just run:

ipmitool chassis bootdev pxe

And your next boot should be a PXE boot.

Edit: This doesn't seem to work for HP iLO2. However, you can SSH in to the iLO2 interface and reconfigure it there by issuing

set /system1/bootconfig1/bootsource5 bootorder=1

On systems that don't support booting from USB key it will be bootsource4 instead. For complete details, see the iLO2 Scripting Reference

You can issue this command as an argument to ssh and that should work as well.

There is a CentOS virtual application that does (almost) all of this already. It's called the Ultimate Deployment Appliance. There's a few things in your list it doesn't support (switching back to the local disk, a proper GUI (it's just a text-based menu) for backgrounds, etc. But I think you'll find that's a limitation of PXE rather than the appliance).

I've been using it for years and it's great. v2.0 (which I see is finally out of Beta) is miles ahead of v1 - so don't even bother with v1.