Is it worth to try to build a FrankenXenon? IMO, no.
What are the possible benefit, more than a rgh xbox360? You can explorer the Xenon build that requires this specific hardware setup.
Is it compatible with retail game? No.
Can I use the extra cpu power/ram? I don't think so.
Can I connect more sata disk and use them for xbox files? No.
Will aurora/fsd/homebrew work? No. Only dev games.
Answering some questions:
Is it worth it? - Depends on the person. I still have multiple FrankenXenons (probably around 4-5) from testing and a few actual Xenon Alpha kits. If you don't have experience with flashing GPUs then you would have to find the X800 XT Mac GPU which is more difficult and pricey (expect $250+ for just the GPU).
Possible benefits - The Xenon OS allows people to mess with early Xbox 360 apps and original Xbox Retail games. It does not have more benefits than an RGH.
Retail Compatibility - The Xenon Alpha kit can run retail ORIGINAL XBOX games but NOT retail Xbox 360 games. Original Xbox games will run very poorly since the emulation wasn't finished at the time.
Using extra CPU power/RAM/HDD - Not possible (at least not by us). Maybe someone with more experience will find a hack someday.
Will Aurora/FSD/Hombrew work? - No. Those apps/dashboards are XEX2 format applications. The Xenon OS on the Alpha kit only runs XEX0 and Original Xbox apps (XBE). There is no leaked SDK that is compatible with the leaked Xenon OS version so homebrew can't really be created for it.
To be absolutely clear to anyone trying to build a FrankenXenon:
The Xenon Alpha Kit is NOT an Xbox 360.
It's a very early version of the Xbox 360 operating system that will only run very early apps created from a very early SDK that no-one has. Apps/games made on release Xbox 360 hardware/software will not run on the Alpha Xenon OS since it was being changed constantly at the time. Even dev games made on the Xenon Alpha OS 0615 are incompatible with the leaked 1529 OS despite them being pretty much the same OS.