I am afraid that Serbian users would have to scroll just as much through this combined board to find relevant topics, as they already have to do in their current local topic.
Two different main sub boards can be created (to solve that issue) there (one for "Croatian topics" and the other for "Serbian topics"). This way it will be well organized.
This seems like an OK solution if we can't get a full separate section, we just need an option to have more then 1 active topic. It's just way to tiring to have one spammable topic, not everybody wants to read the same stuff and if you don't visit the forum every day it's even worse, trying to find the last post that's relative to your interest is not fun at all.