yes, i have tried that already. it will work fine.
you have a couple of options:
debian has support for multiarch, so you can install 32-bit packages in a 64-bit system. there are many docs/wikis out there to help you do that. that will give a mixed system where you can install both 32 abd 64 bit apps
you can create a complete debian rootfs from scratch using debootstrap and make it 32-bit. From there you can add all the components you need to make up your own custom systems
you can use our prebuilt armhf debian rootfs that you can find here: http://snapshots.linaro.org/debian/images/. these are the rootfs we are using to generate the debian image that we release eventually.
In any case you need to use the same 64 bit kernel. We do not support (and do not plan to support) 32-bit kernel for APQ8016 (the SoC on DB410c). But it is possible to run 32bit user space on 64 bit kernel.
If fact if you follow the same build scripts that we use for 64-bit images, and set the rootfs to armhf, you will end up with exactly what you need (e.g. https://git.linaro.org/ci/job/configs.git/tree/lt-qcom-debian-images-arm64.yaml).