Spot instances per process in GCP

Hi Nextflow team,
I'm planning to use cloud-batch executors with Nextflow. Is it possible to specify a spot instance for each process? I want to use non-spot instances for some processes. 
Looking at the following issue, it seems that you can't specify the machine type for flexible, so I'm asking this question.
https://github.com/nextflow-io/nextflow/issues/4657

Thanks,
