All the 4th gen iPod touch units utilize a single nand chip, whether they are 8,32 or 64 GB. The 3rd gen units used a pair of 16GBs for 32GB or a pair of 32GBs for 64GB. Late 2nd gen units had provision for a pair of BGA nand chips (same as 3rd gen), but mostly used only one 8GB chip and rarely a pair of 4GBs for 8GB or a pair of 16GBs in the 32GB unit. Earlier 2nd gen units used single or double (stacked) DIP nand chips.
The upshot of all this is that if a person had two irreparable 4th gen 64GB units with functioning nand, chips these could in theory be transplanted into a late 2nd or any 3rd gen iPod Touch, to create what may well be the worlds only 128GB iPod Touch. Provided the chips were wiped out of circuit, the bootrom should realize the absence of iOS, kick into DFU, iTunes will see it, and restore the firmware... Any thoughts?