As a general comment, I am doing closed loop temperature control on a LV 8.6 system using "bang-bang" control.
PID is almost a "knee jerk" when it comes to control algorithms, but it is a costly item from NI and, at least in my situation, not needed. Not the cost, not the aspirin of working with PID.
"Bang-bang", if it doesn't ring a bell, is the way everything in your domestic world is controlled. Your heater, your air conditioner, your toaster, your oven, your electric blanket (probably). The only proportional control I can find in my domestic world is the engine thermostat on the family car.
"Bang-bang" needs no analog output, no heavy math. The only requirements are that the process driving force (in my example, the heaters) is not over-sized for the problem and that there is enough time in the process.