Hello Dharmakasi,
The system created method gets created in case of normal context node enhancement. Here we probably are dealing with a little different because the Tree Node will have a Proxy class attached to it.
I have resolved the problem on my own.This was achieved by manually redefining the CREATE_IBASE method. Then I required to create a new Z class manually which will be Child class of Proxy parent class.
Post that I have to change the pointing of my new child context node class to start referring to the child proxy class. All this is done manually by changing the relevant code.