2002 audi a3 1.6 overheating problem, macgyver fix?

Context: i bought a 2002 audi a3 1.6 but it has really bad overheating problems, the thermostat is an electronically controlled unit but my (and a garage i brought it to) suspision is that the ecu isnt controlling it. Im not going to replace the ecu because it would be borderline double of what i paid for the car.

So my idea is, i remove the thermostat and replace it with a ball valve on the coolant line coming out of it so i can "regulate" the flow of coolant to the radiator. I know it definetley isnt a long time solution but aslong as i can drive the car 2-3 months i got my moneys worth.

Really dumb? Or just stupid enough to work?

Anybody other ideas i'd gladly hear it