Switch to 256
After re-imaging and expanding the switch nand at least 10 times during the dance to get the switch to see the larger 128GB nand I eventually got it working, but didnt make a note of exactly how I got it to work, damnit! I had to do it again to make some better instructions, and if I had to do it again, I may as well go large, as large as I can find, 256GB!
I dissasembled the switch again, (Thanks iFixit again!), swapped the EMMC board, put it back together and crossed my fingers. Booting into Hekate (the one modified by John to restore to larger EMMCs), the EMMC was seen properly by the switch, success!
Now to get the old data copied over and enlarged.
I restored the boot0/1 backup and rawnand I used last time. (lucky I backed up my savegames before removing the 128gb).
I then followed the same process as before, this time using only gdisk, as I was pretty sure that gparted was messing with the process. After the partition resize in linux, it booted up, a good sign! I mounted the emmc on windows with HacDiskMount and reformated the partition underneath with the command line tool fat32format. I copied back the data and rebooted.. Success! 256GB Switch upgrade worked first time!
I documented the steps and so will make a standalone guide post of the exact commands and process to extend the Switch NAND to help others down the path to upgarded switch heaven!