can you clarify/show an example of what you're referring to ?

you want to replace symlinks with hard links ?  or something else ?

At least by inspecting latest tatl image, this is what I see:

libc for garcon and the rest of tatl have the same contents (expected):
$ md5sum /opt/google/garcon/lib/libc.so.6 /lib64/libc-2.23.so
45a7c5242ec147a447424a8187756ae1  /opt/google/garcon/lib/libc.so.6
45a7c5242ec147a447424a8187756ae1  /lib64/libc-2.23.so

But they don't share the same inode:
$ ls -i /opt/google/garcon/lib/libc.so.6 /lib64/libc-2.23.so 
 69 /lib64/libc-2.23.so  211 /opt/google/garcon/lib/libc.so.6

So unless there's some deduplication happening elsewhere, this is using 2x the disk space for libraries that are shared with the rest of tatl.

that's because garcon was told to output to a unique path with the explicit purpose of being a standalone root to be bind mounted in.  depending on the component process, the filesystem might take care of deduping, but prob better to do this ourselves.

we could write a python script to do it or use fdupes.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/portage-stable/+/54111ee2b1353ce488c4f0cfc75c7e6677e8f208

commit 54111ee2b1353ce488c4f0cfc75c7e6677e8f208
Author: Stephen Barber <smbarber@chromium.org>
Date: Sat Apr 07 05:00:11 2018

fdupes: add 1.51 ebuild from portage-stable

BUG= chromium:826144 
TEST=sudo emerge fdupes

Change-Id: I69fdd7aba460f57c2b1f4e3c2f4e08eef4f19bc3
Reviewed-on: https://chromium-review.googlesource.com/1000840
Commit-Ready: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>

[add] https://crrev.com/54111ee2b1353ce488c4f0cfc75c7e6677e8f208/app-misc/fdupes/fdupes-1.5.1.ebuild
[add] https://crrev.com/54111ee2b1353ce488c4f0cfc75c7e6677e8f208/app-misc/fdupes/metadata.xml
[add] https://crrev.com/54111ee2b1353ce488c4f0cfc75c7e6677e8f208/app-misc/fdupes/files/fdupes-1.50_pre2-compare-file.patch
[add] https://crrev.com/54111ee2b1353ce488c4f0cfc75c7e6677e8f208/app-misc/fdupes/files/fdupes-1.51-makefile.patch
[add] https://crrev.com/54111ee2b1353ce488c4f0cfc75c7e6677e8f208/app-misc/fdupes/Manifest
[add] https://crrev.com/54111ee2b1353ce488c4f0cfc75c7e6677e8f208/app-misc/fdupes/files/fdupes-1.51-fix-stdin-lvalue.patch
[add] https://crrev.com/54111ee2b1353ce488c4f0cfc75c7e6677e8f208/app-misc/fdupes/files/fdupes-1.50_pre2-typo.patch