Think of the market regions as demographic segments. Not as far as I can see. Within the simulation, all existing marketing research is at the regional level, so it may be difficult to find sub-segments within vaporware market regions even if they do exist. First, it's appropriate to begin by focusing on profitability. Volume and market shares are not the only games in town.
Profitability is crucial.
Continue to manage your brands for maximum profitability. Less attractive market regions might be vacated in favor of more attractive regions. In the historical archives of this simulation, there have been cases of successful market leaders who have concluded that a region-leading brand in a small market region would be better deployed in another much larger market region. There are more market regions than brands so choices have to be made. And, there's no rule that says you can't have more than one brand targeted at a particular market region.