In OpenBMC, there is a concept of Fan Zones. A fan zone groups several fans together and control them in a PID loop. Fan zones have an important property: mode, which can either be Auto or Manual to indicate status of PID control. I've searched the Redfish Schema a bit but didn't find a clear way to model such "Zone" concept. We currently use an OEM under the Thermal subsystem to control the mode of fan zones. But we would like a formal way in the Redfish Schema so everyone (in the OpenBMC community) can use it.
We'd like to see a proposal for this, but if this is only for system validation / testing purposes (we don't normally see products allowing users to disable PID loops as that leads to failures and service provider/warranty issues, etc.), it may be sufficient to just add a "TestMode" boolean property on Fan that allows that (perhaps with a "system under test" flag elsewhere to enable that feature).
A "fan group" on its own doesn't describe much more than what PhysicalContext already provides - unless that concept is fleshed out to really show what that group really means (what subsystems is it cooling?).