With regard to RIS, you can place an image of PE on the RIS server, boot PXE to RIS, choose PE, boot PE, then via script map network shares, copy NTFS data up (USMT? not likely), reimage from RIS, Ghost, etc. and then restore data. Possible, yes, feasilbe, TBD.

RIS in this case simply replaces the CD component of booting. I'm unclear on how RIS allows you to boot PE from an image and weather you can boot from any image or if this is PE proprietary. Uncharted territory for me; just going off of the PE documentation thus far.
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-Jim

...the sort of general malaise that only the genius possess and the insane lament.