In Fluent NHibernate 1.3 there's no way to set up key column options other than name in SubclassMap<T> maps for joined subclass inheritance strategy. It'll be useful to define different DDL options, like on-delete, foreign-key, unique, etc.
The only key-related method in SubclassMap<T> is:
public void KeyColumn(string column);
Similiar issue is with Join mapping - there's no possibility to map DDL-level key column options apart for name.
See also: http://notherdev.blogspot.com/2012/01/mapping-by-code-inheritance.html and http://notherdev.blogspot.com/2012/01/mapping-by-code-join.html