While I know your request sounds like a reasonable one. I'd have to say no. Simply, these forums could then easily be turned into nothing but ads for group space, group tours, etc. There would be no way of knowing, or judging, which groups were legitimately looking for others to fill an empty cabin, or if they were TAs simply trying to sell group space.
We have classified ads for that, and people can choose to visit and check them out, rather than filling our message boards with them.
In fact I've deleted some of these types of posts in the past. Not because I didn't feel they were legitimate, but rather to keep the playing field level and the rules for posting clear.
Hope u understand.