One thing about this is that we're looking up helper classes in a path based on the experiment name.  If the experiment name contains characters that don't work well as path names, we'd presumably need to do some escaping.  But, if we do escaping, it makes the path name unintuitive for people writing classes for that experiment.  I.e., seems like we'd need to document "here's the path" more visibly.  That could well be the case anyway.