interesting link.. I didn't know about it. However it's an expensive boot process... LK -> uboot -> ELF file..
LK is all open source software, and anyone can recompile/replace it (and it's ELF too), so for baremetal it should be entirely possible to skip LK and uboot all together. I don't think it's been done yet, but there is no proprietary/closed pieces involved to do it.