I kind of assumed that there would be a /usr/share/uboot/ dir with all the u-boot-sunxi-with-spl.bin and I could just dd the Cubieboard2 uboot with bs=1024 seek 8, but no such directory. And I can't find a Fedora-arm image that has the 2015-10 uboot. Actually it would probably be in a Rawhide image, as F23 has 2015-09 and current Rawhide has 2016-01.
So in your next image, include all of the uboots, or a least a lot more than none. Then we can take the Fedora-installer (which is now an rpm to install on a Fedora workstation, use to be a downloadable zip. Ask Paul Whalen, its author where it is these days) and pretty much use it as is.
At least point me to the Cubieboard2 uboot 2015-10 and I will give it a test spin.
And, yes RPi2 has its own set of differences...