What's the difference between "written it" and "done it"?
I was going to create such relocating loader, but then I was stuck with the case when the old firmware location and the new firmware location overlap and with minimizing memory usage, and with the need of compressing the firmware (to allow executing fw_all.bin through copying it to RAM directly by flashing it with RGN instead of boot.bin).
Then I've got a headache, and stopped thinking about this loader.