Need Non-Mopar Help

I need help with only non-Mopar I have ever owned. It is a 2000 Impala 3.4 L. The thermostat is stuck open. To repair/replace it the throttle body has to be removed. I understand it is abt a 5 hour job. Can I get away with putting an inline thermostat in the upper radiator hose? Are there inherent problems with this? I hate to pay 5 hours labor for the repair and why in the world would they design something like this? Thank you.