[development] Advice on module writing

[John Summerfield]

I've had a look at the domain modules and organic groups and neither 
seems to do what I want.

What I want is to create a domain/site structure like this:
widgiemootha.example.org,
wiluna.example.org,
witchcliffe.example.org
wagin.example.org
wyalkatchem.example.org
www.example.org
birdiya.example.com


Membership between all sites will be shared, but individuals might not 
actually be members of any particular site.

Drupal's multisite allows sharing tables and so membership. As far as it 
goes, that is fine.

Content associated with a site will only be visible at that site.

A site's content at some paths, such as /About will override all others 
at that path.

A site with nothing at /About _might_ inherit from birdiya, the boss 
site. On the other hand, /News might merge news from friends.

Content shared with other sites will be visible at other sites. 
Aggegator is similar in content, but sharing will be explicit.

One idea I have is to extend the node to have two more fields: owning 
site-id, and sharing attributes.

I tried the domain modules, but when I was associated with two sites I 
got two /About menu items, and the implementation shared users behaved a 
little oddly: I want to switch back and forth between sites, maybe by 
choosing them from a list of links, and not to have any problems with 
sessions management or with access.

The first question is, is it in order to modify the node table? I've 
googled and googled and not found an answer to that question.