just
off...
Please don't top-post.
If it's just your embedded device, then you can do whatever you want, if it sort-kinda looks like FAT, great, but nothing else will care.
But a large part of the reason for using FAT is that the device will be accessible by other systems (perhaps the PC you intend to use to download the firmware on to the flash device). And many of those will be unhappy if the "disk" is formatted inconsistently with its physical size.
Or just insist that the flash device is at least 33MB, and you can force FAT32 without trouble.