In reply to UVM_LOVE:
As cgales pointed out your wording is a bit confusing, why not just use config_db to set the RAL model and then in your base sequence you can get it with config_db get (please do not take the code as working example is just an idea)
//In the env class
uvm_config_db#(ral_model)::set(null, "*", "ral_model", ral_model);
// in the sequence
if ( !uvm_config_db#(int)::get(get_sequencer(), "", "ral_model", seq_ral_model))
HTH,
-R