I believe the advanced grammar should be usable throughout the complete snapcraft.yaml. Projects targeting multiple architectures currently requires maintaining multiple manifests for multiple architectures. An example pain point is, consider, there are 3 services, only 1 needs to run in both amd64 and arm64, the other 2 are exclusive to only one architecture, how can one handle that? ```yaml app1: command: app1 daemon: simple restart-condition: always restart-delay: 5s app2: command: app2 daemon: simple restart-condition: always restart-delay: 5s after: - on amd64: - app1 app3: command: app3 daemon: simple restart-condition: always restart-delay: 5s after: - on arm64: - app1 ``` I believe this should be fairly simple. Also, another scenario, where I just don't want to build a particular part in one architecture, currently I'll have to do this ```yaml part: override-build: | if [ "${CRAFT_ARCH_BUILD_FOR}" == "arm64" ]; then echo "skipping..." else craftctl default fi ``` But I think this not really a very clean solution. Also, I believe using the advanced grammar on keys like cmake-parameters is also essential and is fairly simple. The current solution is very hacky ```yaml part: cmake-parameters: - -DPI=${PI} - -DX86=${X86} build-environment: - on arm64: - PI: "ON" - X86: "OFF" - on amd64: - X86: "ON" - PI_SNAP: "OFF" ```