Extensions for directories

Is there a mechanism for getting the Extensions editor to allow for general  
purpose extensions on directories?

I'm wanting to utilize the .htmld to represent directory wrappers for html  
sources trees.  Logically this means having an index.html inside of the  
blah.htmld director with all references being local to that source point.

Unfortunately, when trying to add an extesion with a class of  
w3c.jigsaw.resources.DirectoryResource, the Extensions editor returns a  
document with no data, thus no way to assign the appropriate attributes.

jas