It makes sense if you take in account that you're packaging the whole stack in a container. It's the same than when you make 'golden images' for a VM with Packe

It makes sense if you take in account that you're packaging the whole stack in a container. It's the same than when you make 'golden images' for a VM with Packer or whatever tool is available: you end up with a platform specific image. But you aren't far fetched at all with that idea you have, and can be done using a Docker multi-stage build: You build all your application with whatever platform you have (either locally or for CI), and then you import your application layer from an ARM64 image in one side, and from and AMD64 in the other. We aren't still very used to multi-platform development environments, so the tooling isn't still perfect (at all).