Yeah I can imagine that situation there ain't best, with having to use one thread for various topics and conversations but it is what is, as others communities had to go through the same thing in the past before they got their local board.

If I am not mistaken I think that you already have a topic with local board request here in Meta section so first step towards your goal has been done. All you can do now is to remain active as a community, write good posts and hopefully one day you will get your own local board. Since it's been a while from the last local board being added, you will have to be patient as it won't happen overnight.