Are these functionalities often used?

Hello all,

I want to implement an XSD tool, and in a first version I would like to 
drop functionalities that are not really used in real life. That's why I 
want to have advice about which features could be dropped in the first 
version:

- any (processContents? namespace?)
- anyAttribute (processContents? namespace?)
- keys
- NOTATION
- redefine
- final and block attributes
- abstract complexTypes

Thanks for your answers.

Michael.