>Raspberry Pi on 16GB SD card
>Plugs in 2 flash drives for space, one 8GB and one 32GB
>8GB is allocated entirely for swap
>32GB is separated into 3 partitions and /etc/fstab edited to mount them on /home, /opt and /usr
>Moves files to the proper partitions on stick
>Kernel panic on boot before keyboard is enabled, kernel panic data taller than screen
>No R/W FS for kernel to dump to
fuck my life

Just one quick question...... why?

USB flash drives are reliable as microsd cards.
The bus is the same so,
just keep everything on the same "drive".
In pi3 you can even boot from usb so you can just recycle an spare hdd drive that you have.

You done fucked something up, because errors while mounting fstab entries send you down into emergency / maintenance mode, not kernel panic
I suspect you did something to your root partition
Mount the sd card somewhere and check if you have Syntax errors in your fstab, also chroot and updating the initramfs would be a good idea
If in doubt, update-grub
Drives in fstab should be referred to using the /dev/disk/by-id/ links
Make sure you're not drawing to much current from the usb ports (a small lightning icon appears in the upper right corner if the pi detects a shortage)

@shelladdicted because I need the slim form factor that slim USB sticks and micro SD give me

@Kimmax Didn't touch the root. fstab was formatted right, I installed with NOOBS so i dunno where grub's config is and I bought Adafruit's 2.1 amp switching supply so I have more than enough power for those 2 sticks, a fullsize keyb and a travel mouse