Typically to measure the predictive power of a model, R^2 is more useful than RMSE because a RMSE score isn't very meaningful without a basis of comparison. If you are using mean absolute error (MAE) instead of RMSE however there doesn't seem to be any R^2 analog I can find in the literature. It's easy enough to define one, but I haven't been able to find a name for such a measure
The closest I could find was mean absolute percentage error (MAPE), but that seems to mostly be used in forecasting, and the mean isn't subtracted in the denominator as it is in RMSE.
Is there a name for the measure I have described, or is there a good reason not to use it?