Just to let you know, your tool works fine on the 501 ICS update (using the full 4 file install method) NVFlash to patched bootloader.
One thing I noticed, you have to use the remounter often, as the /system will lose RW and revert to RO after using an application. So it seems to be temporary.
Example; Use remounter to get RW on system. Open Root Explorer and change System to RW. Do your business. Close Root Explorer, come back a few minutes later, and you have to use remounter again.
Minor annoyance, but will probably need looking into.
Nice tool though!