Makes no difference, there was still a goverment in exile in England.
The king was considered 'in no position to rule the belgians'.
This is one thing that would be accuratly portrayed in HoI3. The germans defeat the belgian army in europe, national unity collapses, a goverment in exile is formed. The goverment in exile keeps control of Congo. Germany occupies belgium.
Are you sure about that? It seems to me that if you loose the national unity you surrender that's it. If, instead, you have a high national unity, as you said, a government in exile is formed. So in the case of Belgium the national unity should be very high because I cannot see so much IC in Congo.
PS
I think that you opened a door on the "fake" governements in exile like Free French. They had no land (almost) and no representativity (in 1940).