For exactly that reason, we actually change $HOME in strict snaps so it matches $SNAP_USER_DATA, so in theory it won’t have to do anything else. Did you find any issues doing that?
The snapcraft.yaml file looks very reasonable. The only thing that might optionally be changed is perhaps to move the plugs to the global scope, since every application is already using them:
This works as long as they’re indeed needed for every application. Once applications require differences, then they must be locally declared again.