Yes, i would have to agree that having a more prominent place for the recent posts (or topics in which was posted) would be more common and perhaps help with its popularity (although i don't like changes very much).
For a solution to the sub-forums, have a look at f.i. this French site here
which houses much more platforms and programming languages. They use a 'front-page' that display the newest posts, e.g. forum display is not on the first page. The complete layout as used there might be a 'bit' overkill for here, but it does give some idea's about common problems encountered and how they could be solved/approached.
What i really miss is more integration with modern media solutions available. One of the things i f.i. like about OS4 coding
is that it kinda integrates/combines forums with blogging with wiki etc.
From a developers point of view: i don't have time to find all kind of solutions for the things i probably would like to express, but don't want spend time finding them, register to them, figure out how they work etc. before i can even begin to f.e. add an item to a wiki or make a blogpost.
One integrated place to rule them all, in which the topics are entwined so that the reader don't have to struggle through all the posted spaghetti to be able to find what he/she really needs.
But such things require a fair amount of investment, software-, coding-, and time-wise that such integrated solution starts beginning to look like a real utopia...
Maybe start with something like you suggested ? :-D