Rather than trying the following, I thought, "Why not ask first?"

Due to the sizes of various hard disks in my machine, I want to move /gnu
to /directoryondifferentdisk/gnu
and then do
mount --bind /directoryondifferentdisk/gnu /gnu

(I have already formed a superstition that
ln -s /directoryondifferentdisk/gnu /gnu
won't work)

I see a vast collection of hard links in /gnu/store/.links...

I forsee problems when copying /gnu, not reproducing hard links
but reproducing the data.

Are my fears founded? How to proceed?
Or better to start over with new installation of gnux and /gnu?