Now I'm really puzzled grub2 as a "search by fs uuid" command that linux is unable to deliver for the root device!
The key word here is "unable". The maintainers aren't *unable* to do this. They are *unwilling* to do this. I don't recall the precise discussion, but basically it boils down to the fact that early userspace (aka initramfs) can do this efficiently, and it needs to be supported in initramfs for other reasons, so it is pointless to duplicate this code in the kernel. I'm sure block folk will chime in if this isn't a fair representation (my apologies in advance if so).
Try dracut. Seriously. It's lean and mean just for this use-case, and you'll be protecting yourself against future changes in the block layer. And you can put root=LABEL=foo on your kernel command line to match your fstab.