Would you mind to comment your code a bit? For me as a person with programming experience, it's not obvious what the code does!

I want to install Ubuntu to mmcblk0p4 (5GB) and try different kernels (with u-boot). Can you provide necessary steps for booting into it, or add options in your script for using an existing partition? backupmenu gives access!

Most of the installing time is probably uncompressing the nemo image, why not install the files otherwise?