Threads have to be created in a forum ... do you only have 1 forum ?
Would you be OK with all new threads being created in a general/catch all forum ? It would be quite the hodge podge.
I could see many forums cringe with your suggestion .... they would say there are already too many threads and encouraging people to post like this is unlikely to help. Why would your forum be different ?
I guess this might be more of interest to my specific forum but who knows.
we run a wiki and forum, two different sites. As such we implemented a "discuss on forums" link on the wiki articles that search the xenforo forums, usually showing a good amount of threads. But in the case where the result is none, it would be nice to retain the wiki visitor and convert them to the forum as a poster.
With that in mind, perhaps the following is a better flow.
Search for "cats" if results are "No results found" than it shows button "create thread about "cats"" Click on the button, login or register, select which forum to post thread in and go for it.