Rabids right, having a v1.0 bios added as a launch wont prevent you from being able to boot into Xenium OS. If you tried to launch the TSOP bios once XOS had booted yeah then you'd probably have troubles. All you'd have to do though is delete the MS bios as a launch item then add the 1.6s MS bios as a new launch item.
As to the why the chip wont load....
when you say you've done the LPC rebuild, do you mean that you've done it the old school way by soldering additional wires or have you just used the white SP adapter (recommended)? If you're using the white SP adapter, Id say you need to check the contacts are ok (as indicated by the 5 LEDs on the adapter), I'd recommend getting some denatured alcohol and cotton tips (chemist) to clean the laquer away from the surface of the motherboard.
If you're not using the SP adapter (which by the sounds of it is th case) and have soldered in additional wires, then you should re-check any connections you soldered, as well as pay particular attention to the d0 connection.