Yeah . You can go crazy with all this stuff. I'll take career ERA as the best yardstick in evaluating a pitcher . It is not perfect . If you want to alter it by considering altitude, wind velocity, temperature, humidity, short porches , green monsters , rafters , death valleys , length of grass and so forth , have fun . We can have ERA + , ERA - , ERA *** , ERA x , ERA y , ERA z and on and on ad nauseum .