We are currently unable to break a host or set of hosts to enable a feature say RUM feature only on one or specific hosts with in one group.
Better to have that feature and it will help to control EUM and costs to the enterprise.
You can always setup host-groups to break a set of hosts and process groups. This will enable you the features you requests.
However, disabling RUM for a host may have an impact on the RUM functionality as the endpoints or inject will not work on all nodes. Depending on your architecture and load balancing you may experience incomplete data or even broken a broken application.
RUM cost control can be defined in the application settings. If you are trying to do it on the process or ost level by disabling the feature, then it's conceptually a wrong approach.