This suggestion arises out of the feminism boards rearrangement - some people like two boards but many want to see all feminist threads at once. I think this would better accommodate all users and reduce some of the discontent.
I believe it might be useful elsewhere, eg Education. Most parents are interested in the stages their DC are at, others may be interested in all of them.
Another possibility (though i'd guess would take quite a bit more to implement) would be if we could have a 'favourites' view so that we could see all threads in our favourite topics at once - mine would include both feminism boards, gardening and HE at the moment,
Starting a thread while in a non-specific view should be fine, just fill in the topic title as happens already if you start a new thread while in active or threads I'm on etc.
If this is technically feasible, I can't see any downside.