You can clone with
In our project we have a lot of classes that are already mapped by "traditional" method - hbm.xml file for each class. In new subprojects we started to introduce fluent nhibernate and encountered the problem - one can not map fluently a class that should be a joined-subclass of a class mapped with a file.
Generally it shouldn't be a problem. In configuration XML it is possible to separate sublclasses to different files.
I'll take a look, but if it's possible to do it, the solution is unlikely to be included in next planned release