It'd be really great if you guys had an implementation of Friedman's Multivariate Adaptive Regression Splines[1]. For me, this is the only R package left for which I don't have a Python alternative.
I did not know about MARS, do you have any practical benchmarking dataset / sample tasks where MARS is state of the art? What kind of regression problem do you use it for yourself? What is the typical dimension of the problems it can address efficiently (n_samples and n_features)?
I'd actually be very interested in such a model. It's a major amount of work, and in an area in which I am not expert, so I know that I will not be working on it any time soon, but I agree that it would be a great addition to the scikit.