The Nash-Sutcliffe efficiency , Willmott's index and Model Performance Index (MPI) are suitable indices to add XLSTAT for assessing model performance.

affordable and simple option for making word clouds for instance...

I think XLSTAT provides partial least squares models but not general least squares. This would be very practical for time series analysis, for instance.

A good idea would be to pay only for a few functions..

So that people won't need another software

Spatial Autocorrelation Indices (e.g Moran's I) are mainstream of spatial statistics that are worth being implemented in XLSTAT software. They are useful for ecological studies.

Estimating lagged prediction models from autocorrelated historical data is a common challenge in business and economics. The resulting multicollinearity causes the models to perform poorly. The Almon lag method is a clever way to deal with the mul...

Would be nice to be able to integrate the area under the curve in linear and non-linear models.

R(ecency), F(requency), M(onetary value) analysis segments customers on their actual purchase behavior. It allows for identifying loyal customers, lost customers, at-risk customers, etc., which can be useful for devising market penetration strateg...

We do a lot of ranking. From the ranking study, we can calculate r-index. Also d prime can be calculated from r-index. I believe there is a package in R already exist. It would be good to add this to XLSTAT.