ln -s /emul/ia32 /emul/ia32-linux
That should make it easier on the installer, and anything else expecting the normal path from the ia32-libs package. Shouldn't cause any problems to your chroot either.
Debian Sid AMD64 here too btw.
Personally i just use the ia32-libs package instead of a chroot. The system defaults to 64-bit libraries, and only falls back to 32-bit libs for 32-bit apps, ld copes very well with the mixed environment. Occasionally i have problems with missing 32-bit libs, for things like Maya (still no 64 bit release yet), but that's easily fixed by unpacking the associated Sid i386 deb to the /emul/ia32-linux root dir.