Mount iSCSI, install from USB

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Hi all,
I have been playing around with iPXE for a couple months now. Nothing mission critical, just exploring different things in my home lab. I have two Windows 10 machines booting over iSCSI, and my HTPC boots over NFS. Pretty neat stuff.
I have a new challenge that I created for myself, and I can't seem to find much information on it...
I'd like to add an iSCSI LUN to my HTPC to boot from, but the catch is that I can only get the installer to boot over USB. The OS is called Lakka. Appears to be loosely based on OpenELEC.
Ideally, I'd like an iPXE script to start by mounting the iSCSI LUN, then boot from USB while leaving the LUN mapped. This would allow me to install to iSCSI, then boot from the LUN after the installer completes.
I know normally it's best to have something started, and ask for direction on what to do next. Maybe provide an example of my script and ask for advice, but I don't really have much. From what I've read, this doesn't seem possible, but at this stage I'm too stubborn to accept that.
Anyone have any thoughts on how this might be done?

Thanks!