The flow control valve is used on the Case/Ingersoll tractors primarily for the purpose of setting and maintaining fine travel speed control.
Specifically, a flow control is a pressure compensated valve which is designed to meter a continuous FLOW rate (gallons per minute) of oil to a working circuit.
(Continuous is really a maximum ... you've got to have speed/flow from the pump to get up to the max flow set on the FCV).
In the Case/Ingersoll application, this is inserted prior to the travel control valve, thereby assuring a specific maximum amount of oil will go to the TCV. You can, for example, dial down the oil rate to the TCV to 1 GPM, regardless of engine RPM and pump output. Then you can throw the travel speed control wide open and get great pulling pressure/torque, but always be at a slow speed (e.g. about 1/8 of the normal 8 GPM top speed).
This is great for tilling, as you often wish to move quite slowly, but the drag load varies considerably, constantly changing the drive motor pressures, so it is quite hard to finesse with the speed control lever.
I can certainly envision usages for this in your application, but frankly would not further compound the hydraulics on that tractor. You cannot use this valve like a priority flow valve. Due to the pressure compensation circuitry in the valve, the excess oil cannot be ported downstream to a working circuit ... only to reservoir return oil.