I think Classbox is the better way to go, but this is an improvement. The performance hit is currently very significant, but I suspect it can be optimised to a

I think Classbox is the better way to go, but this is an improvement. The performance hit is currently very significant, but I suspect it can be optimised to a negligible level. As with the .append_features hack, I think it is only good that refinement in no way implies inclusion. It will probably be better to keep the two types of modules explicitly separate.