Create a hook in og.module for og_is_group_member/admin functions

This allows other modules to control the group memebership/admin status based on module specific code, dynamically at page load time.

I have coded these modifications to my local version of OG.
The current behaviour follows the drupal access pattern. Modules may False/Deny access, which supercedes True/Allow access. If no modules implement the hook or all modules return null, then the default behaviour takes place ($user->og_groups....)
There is no priority weighting.

Questions:

1. Is this a useful idea, or have I missed something completely?
2. If is it useful, would you like a patch for 6.x dev?
3. Does this functionality exsit for og_d7?
4. I have a bunch of other modifications I am making using this hook and og_subgroups for some pretty otb functionality for "drupal as a framework" which I would like to share with the drupal community when finished. I think it would be useful for D6 and D7, and many people are stull using D6.

Feedback Appreciated.