No, it won't work without uBoot modifications.
$this->bbcode_second_pass_code('', '
fw_setenv usb_scan_1 'usb=0:1 dev=sda2'
fw_setenv usb_scan_2 'usb=1:1 dev=sdb2'
fw_setenv usb_scan_3 'usb=2:1 dev=sdc2'
fw_setenv usb_scan_4 'usb=3:1 dev=sdd2'
fw_setenv usb_rootfstype ext4
')
This is probably the easiest solution. Different approaches can be found
here and
here.
Also note that after you have moved the /boot folder to the first partition and booted the plug, the kernel image will be located in /boot/boot/uImage, but when you update the kernel, the new image will be installed in /boot/uImage, i.e. in the root folder of the first partition. If you do not move the new image to /boot/boot/uImage, then uBoot will still start the old kernel.
My suggestion is not to move the /boot folder to the first partition, but only to move the contents of the /boot folder to the first partition, then change to the root folder of the first partition and create a link
$this->bbcode_second_pass_code('', '
ln -s . boot
')
This way uBoot will always load the currently installed kernel image.
I also don't think using ext4 with journal should be limited to hard drives, as I have already mentioned
here.