I can answer only for 2.0beta

Because the validator on previous Cook 1.5 is not handled very well.

The rules ares missing in Cook 1.5 and JDom create a kind of work that is now done with the rules (2.0)
So, if you really want to use Cook 1.5, generate it without the validator, and then config your validator manually reading the documentation of it. (little bit of JS config, few lines)

EDIT :
Cook V2.0 beta is now using JInput and do not handle anymore 1.6, 1.7.
I would like it possible so I am working on that during the beta process. In priority list.