Although, I do like the idea of keeping it forum centric. Local sections tend to have tighter knitted communities, and this is evident on how they vote at times. They usually include users from their local sections.
This is another relevant point, which there is no way to control.
It is normal for local tabs to have their own dynamics and to carry out certain types of events, which only have a local impact. And it is also normal for local members to get to know each other better than in a more global way.
So it's easier for me, for example, to choose members from the Portuguese tab than other members. Despite trying to look for members in general, who can fit into each category.