You can call stan_model to compile the Stan program and then call sampling, but I don’t think that is going to help you much.
If you call stan or sampling specifying pars = character() and sample_file as some path, then you are basically doing CmdStan. Then you have the problem of how to read the draws off the disk with the available memory. The read_stan_csv function does not have an option to read a subset of the parameters.