You're right that it doesn't allow that directly, though it can be done with some work if you know what you're doing.
A bigger problem is that trying to run 32-bit binaries with non-trivial library dependencies on Debian is an exercise in pain. Debian's 32-bit support is *really bad*. Most libraries don't have 32-bit versions available, and those that do are just the binaries rammed into a couple of huge ia32- mega-packages.
There are proposals and frequent discussions about multilib, but no visible progress (unless you count major breakage for a month or so earlier this year), and it's one of those subjects which is practically guaranteed to start a flamewar if mentioned on debian-devel.