additional forums edit permissions

to go with the "edit own comments" permission feature request: http://drupal.org/node/79693

Would it be possible to have an "edit, but not delete, own forum topics" permission?

This would mean that if someone makes a typo in their original forum post, they could fix it, but they can't then delete the entire post and all subsequent comments if a discussion doesn't go the way they want (or even worse by accident)!

In other words, split "edit own forums topics" into:

edit own forum topics
delete own forums topics

Alongside that, we're looking into having moderators for specific forums using taxonomy access control. To do this, the best way I can see is to give moderators and "edit all forum posts" permission, then define "update" permissions for specific forums via tac. I can't currently see a way to have forum moderators without giving them "administer nodes" - or "administer comments" - which both bypass access for elsewhere.

So forum permissions would then be:

administer forums
create forum topics
edit own forum topics
delete own forum topics
edit all forum topics

We're trying not to hack anything in core too much, so thought it worth asking at least!