You're right about the ability to comment, but it doesn't save you from the tedious commas:

  drive_args=(
      file=/export/cirros.qcow2,
      format=qcow2,
      if=virtio
  )

  qemu_args=(
      -display none
      -m 2048
      -serial stdio
      -drive "$(printf "%s" "${drive_args[@]}")"
  )

  qemu-system-x86_64 "${qemu_args[@]}"

Personally, I prefer it with the backslashes if I don't need to comment.