sometimes it'd be easier to just search through those threads and ignore the off topic links until i have time to read through them
Then use the 'New Posts' link/button - this will list the currently active threads and it should be fairly obvious which are about site design. Mike has also provided a clever facility on the main site page that shows 'hot topics' so I still think that between these two features it's only essentially a click or two and a little skimming on your behalf in order to find those threads relevant to your current interest.
I'll also edit my post above to reflect those threads that seem to be relevant to site design.
Or a sub-board?
I'm still disinclined to create a new forum for something that will be transient at best (okay, there's a lot of activity now but that won't always be the case once the main content has stabilised).
Still, if there's a huge and popular outcry/demand for it then it can obviously be done.