You do not necessarily need MO privileges in order to stop actions. With v9.5.5+, you can configure operators to be able to stop other operators’ actions (assuming the same computer mgmt rights). Please see https://help.hcltechsw.com/bigfix/9.5/platform/Platform/Console/c_adding_local_operators.html for more information.
Given this, one potential option is to have a non-master operator with the ‘Stop Other Operators’ Actions’ set to ‘Yes’, and assuming it has the same computer mgmt rights (or a superset), then its credentials can be used remotely via REST API rather than a MO. Additionally, this non-master operators doesn’t even need to be able to deploy actions (i.e. ‘Can Create Actions’ can be set to ‘No’, and it will still be able to stop other operators’ actions).