I would like to see this too. I have a website I started with dnnBB and it would create unique forum instances based on the moduleID. So what I did was changed it so that by default it would display the forum based on moduleID but if you passed in a new module ID parameter (in my case m=xyz), it would use this new one instead.
This is what I would like to see. Where you can pass in the forumID in a query string and it would display that forum instead. I suppose there are security issues here though. In my case, I am sharing forums across portals too.
I love the new DNN forums. I may try to migrate to it sometime down the road I think....
Jason