Right now, when we have many sub-forums, viewing the threads present into parent forum can become challenging. Here it is an example:
Now, imagine that you have 10 sub-forums, instead of 4...
An elegant alternative to this issue will be to use the current button popup present into forum home page that lists the existing sub-forums, when you hover over it. All we would have to do is increase a little the font and locate it right under the Post New Thread button.
To see what I mean, go to XenForo forum home page and scroll down until you find the Development Tutorials and Resources forum. Right underneath, you will see the sub-forum link. Imagine that exact type of link displayed under Post New Thread button. I think it will look great.
That will make the current forum display very compact and users will be able to enjoy what they want most: read the threads, not have their screen filled with a list of sub-forums. Plus, it will allow to keep the Post New Thread button into same location, not under the list of sub-forums like it is now. Not to mention that is innovative, it will be different from any other forum systems that replicate always and always the same design.