Extend NAC with private_nodes / buddylist2 functionality

The idea of private_nodes - AFAICC - finds a better solution here with NAC.
But there is a nice things together with buddylist (not working with buddylist2):
having buddylist installed you can set your nodes visible to all your buddies.

now, how could that get into NAC in a propper way?
To me this is really a question. Is is better to
- extend NAC or
- make up a new module that depends on NAC?

I did not write an own module yet so I am not experienced for that question.
Hacking around I would take NAC. But is that a good way?

What I would like to see with this extension is this:
Having buddylist installed and having buddies
- there is a kind of table to set checkboxes for
-- all my buddies at one
-- some of my buddies
-- some other users that are not my buddies

The functinality is the same as chosing one user and grant him rights to my content.
(But - sorry - this way takes quite some time, and has the need of saving it after one more page reload)
For an easy way there is needed only a list of my buddy users with check boxes for the grants.
The overview table is a different thing.

SO:
Shall I make a new module out of that?

Axel